Camera system operable by carrying data from a camera accessory to a camera body

ABSTRACT

A camera system operable with data carried from a camera accessory to a camera body. The camera accessory has a ROM for storing various data at a plurality of addresses, respectively, each of which data consists of a plurality of bits, and a coupling terminal for receiving a train of clock pulses from the camera body. A circuit is also provided for sequentially designating the address of the ROM one by one to permit the ROM to output data stored at the designated address. In the circuit, an address signal is formed in response to the clock pulses, received through the coupling terminal, for designating an address. The data derived from the ROM are transmitted to the camera body.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention generally relates to a camera system comprising a cameraaccessory such as, for example, an interchangeable lens or a lensconverter, and a camera body to which the camera accessory is coupledand, more particularly, to a camera system operable by carrying data,stored in the camera accessory to the camera body. This invention alsorelates to an improvement in the camera accessory or the camera body ora combination thereof utilizeable in the camera system of the typereferred to above.

2. Description of the Prior Art

There has been well known a camera system comprising a camera accessoryadapted to be coupled to a camera body and provided with an informationstoring and memorizing circuit (hereinafter referred to as a ROM) whichstores various pieces of information peculiar to the camera accessory(for example, the maximum and minimum aperture values of aninterchangeable lens in the case where the camera accessory is theinterchangeable lens), so that desired pieces of information of thecamera accessory can be read in the camera body by specifyingcorresponding addresses in the ROM. However, the practical design ofsuch a system involves numerous problems.

In the first place, in the system of the type described above, aplurality of coupling terminals are necessary to electrically connectthe camera accessory with the camera body for the transmission ofsignals therebetween. A control circuit for controlling the transmissionof the signals between the camera body and the camera accessory throughthe coupling terminals is also necessitated. However, in terms of thereliability, the smaller the number of the coupling terminals, thebetter. Yet, it is desired to render the signal transmission controlcircuit to be compact in structure. Moreover, since the signals to becarried from the camera accessory to the camera body are diversified,specific counter measures therefore are desired to be embodied. Acounter-measures is also required to render the camera body to cope withthe camera accessory having no data to be carried to the camera bodywhen it is coupled to the camera body.

Hitherto, however, those problems have not been solved and, even ifsolved, are solved unsatisfactorily.

SUMMARY OF THE INVENTION

Accordingly, this invention has for its essential object to provide animproved camera accessory and/or an improved camera body having theminimized number of the coupling terminals.

Another object of this invention is to provide an improved cameraaccessory and/or an improved camera body wherein improvement is made toenable the camera body to read the data from the camera accessory.

A still further object of this invention is to deal with the diversifieddata stored in the camera body.

A still further object of this invention is to provide the structurenecessary to carry the data from the camera accessory to the camera bodyin the event that the data consist of a plurality of kinds of datavariable with a piece of information set in the camera accessory.

A still further object of this invention is to provide an improved zoomlens assembly capable of transmitting information indicative of a changein effective aperture value thereof when the camera accessory is used inthe form of the zoom lens assembly of a type having the effectiveaperture value variable with the zooming, and also an improved camerabody operable upon receipt of the information.

A still further object of this invention is to deal with the change ineffective aperture value which would result from the use of a lensconverter, which is one of the camera accessories, between the camerabody and the interchangeable lens assembly which is also another one ofthe camera accessories.

A still further object of this invention is to provide an improvedcamera body and an improved camera accessory both operable bytransmitting data indicative of the time required to effect the controlof the aperture of the interchangeable lens assembly which is one of thecamera accessories.

According to one feature of this invention, address signals foraddressing the data stored in the ROM in the camera accessory are nottransmitted from the camera body, but are prepared in the cameraaccessory in response to clock pulses fed from the camera body.Accordingly, the numbers of the requisite coupling terminals can beminimized.

According to another feature of this invention, a counter for countingthe clock pulses fed from the camera body is provided in the cameraaccessory and the address signals are prepared in correspondence withthe contents of the upper bits thereof. On the other hand, the contentsof the lower bits of the counter are used to control the serial feed ofthe data in the ROM addressed to the camera body. This serial data feedcontributes to the reduction in number of the coupling terminals.

According to a further object of this invention, the clock pulses aregenerated in a predetermined number in response to each read-ininstruction generated from a micro-computer in the camera body, whichread-in instruction is repeated in a number of times.

According to a still further object of this invention, in the event thatthe data variable with a piece of information set in the cameraaccessory are available in a plurality of kinds, these data are storedat different addresses of the ROM and one address signal is designatedby a signal fed from the camera body for determining the kind of thedata and the information set in the camera accessory. With thisconstruction, the circuit for the control of the signal transmission canbe simplified. Examples of the information set in the camera accessoryaccording to this feature include the focal length of the zoom lensassembly whereas examples of the data variable therewith include theeffective aperture value.

According to a still further feature of this invention, the informationof the effective aperture value variable with change in focal length isstored in the zoom lens assembly and is transmitted to the camera body.Upon receipt of this information, the camera body utilizes it for thecalculation of the stop-down number and the calculation of thethrough-the lens (TTL) measured information to compensate for an errorresulting from change in focal length. In the case where the TTLmeasured information is AE-locked, different pieces of information ofthe effective aperture values are utilized for the calculation of thestop-down number and the calculation of the TTL measured information,respectively. According to a still further feature of this invention,even when the change in effective aperture value occurs as a result ofthe lens converter, this change can be compensated for during thecalculation of the stop-down number and that of the TTL measuredinformation. In the practice of this invention, examples of the datathat can be stored in the camera accessory include, in addition to thatreferred to in the foregoing, data of the time required for the controlof the aperture with which in the camera body, the difference in timingbetween the time at which the aperture is stopped down and the time atwhich the mirror is cleared or shifted up can be controlled. Accordingto a yet further feature of this invention, whether or not the cameraaccessory is of a type having data can be discriminated in the camerabody by the identification of the particular data, whereby the mode ofoperation performed in the camera body can be automatically switched.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and features of this invention will become clearfrom the following description taken in conjunction with preferredembodiments thereof with reference to the accompanying drawings, inwhich:

FIG. 1 is a block diagram showing an electric circuit incorporated in aphotographic camera body, FIG. 1 being composed of FIGS. 1(a) and 1(b);

FIG. 2 is a block diagram showing an electric circuit incorporated inany one of lens adaptors which can be utilized in combination with thecamera body having the circuit of FIG. 1;

FIG. 3 is a block diagram showing an electric circuit incorporated inany one of interchangeable lens assemblies which can be utilized incombination with the camera body having the circuit of FIG. 1 with orwithout the intervention of the lens adaptor having the circuit of FIG.2;

FIG. 4 is a schematic diagram showing a data setting member togetherwith an associated electric circuit;

FIG. 5 is a circuit block diagram showing an exposure control unitincorporated in the camera body;

FIG. 6 composed of FIGS. 6(a), 6(b) and 6(c) is a flow chart showing thesequence of arithmetic calculation performed by an exposure arithmeticcircuit used in the circuit of FIG. 1;

FIG. 7 is a circuit block diagram showing an exposure control unitincorporated in the camera body;

FIG. 8 is a block circuit diagram showing a modified form of theexposure control unit;

FIG. 9 is a block diagram of a circuit suited for the exposure underflash lighting;

FIG. 10(a) is a block diagram showing a circuit incorporated in thecamera body according to another embodiment of this invention;

FIG. 10(b) is a block diagram showing a circuit incorporated in the zoomlens assembly according to another embodiment of this invention;

FIG. 11 is a circuit block diagram showing a serial data read-in unitused in the circuit of FIG. 10(a);

FIG. 12 is a timing chart showing the operation of the circuit of FIG.11;

FIG. 13 is a chart showing the waveforms of various signals appearing inthe circuits of FIGS. 10(a) and 10 (b);

FIG. 14 is a flow chart showing the sequence of operation of amicrocomputer used in the circuit of FIG. 10(a);

FIG. 15 is a time chart used to explain the exposure control operation;

FIG. 16 is a perspective view of the camera body and the zoom lensassembly, with the zoom lens assembly shown as separated from the camerabody.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Before the description of this invention proceeds, it is to be notedthat like parts are designated by like reference numerals throughout theaccompanying drawings.

Referring to the drawings, FIG. 1 illustrates an electric circuitarrangement incorporated in the body of a photographic camera, FIG. 2illustrates an electric circuit arrangement incorporated in any one ofthe lens adaptors which can be utilized in association with the cameraembodying this invention, and FIG. 3 is an electric circuit arrangementincorporated in any one of the interchangeable lens assemblies which canbe utilized in association with the camera embodying this invention.Referring particularly to FIG. 1, the circuit arrangement shown thereinincludes a source of electrical power BA, constituted by, for example,one or more batteries, and a light measuring switch S1 operativelycoupled to a light measuring button (not shown). When this switch S1 isclosed, a transistor BT1 conducts to allow an electric power from thepower source BA to be fed through a power line +V to both a power-onreset circuit 1 and an exposure control unit as will be described later.The power-on reset circuit 1, when fed with an electric power throughthe power line +V, generates a power-on reset signal POR to reset aflip-flop FF1, registers REG 2 to REG 13, a D flip-flop DF1 and adivider DI1. All of the counters, flip-flops, registers, decoders andother circuit components shown therein are supplied with the electricpower from the power source BA through the power line +E.

On the other hand, an inverter IN1 generates a high level signal inresponse to the closure of the light measuring switch S1, and when aclock pulse CP is applied to the D flip-flop DF1 from an oscillator PGwhile the output from the inverter IN1 is in a high level state, the Dflip-flop DF1 generates a high level signal from its Q output terminalin response to the positive edge of the clock pulse CP. In response tothe high level signal from the D flip-flop DF1, an AND gate AN1 isenabled to allow the passage of clock pulses CP therethrough to thedivider DI1. The high level signal from the D flip-flop DF1 is also fedto a one-shot circuit OS1 to cause the latter to generate a high levelpulse for a predetermined time, which is in turn supplied to theflip-flop FF1 through an OR gate OR1. In response to this high levelpulse, the flip-flop FF1 is set with a high level output consequentlygenerated from the Q output terminal thereof. At this time, a flip-flopFF10 is reset by the power-on reset signal and, therefore, an AND gateAN40 is enabled to allow the passage therethrough of the high leveloutput from the flip-flop FF1. This high level output emerging from theAND gate AN40 is a start signal to be fed to the body of thephotographic camera as well as a particular accessory for initiating theread-in operation.

In response to the start signal, an AND gate AN2 is enabled and,accordingly, counters CO1 and CO2 are released from reset conditions tobring a decoder DE1 in a condition ready to generate its output. Thecounter CO1 serves to count the number of clock pulses CP fed theretofrom the oscillator PG through the AND gate AN2, and the decoder DE1serves to render one of the output terminals TB0 to TB7 in a high levelstate depending on the output from the counter CO1. The relationshipbetween inputs and outputs of the decoder DE1 is tabulated in Table 1below.

                  TABLE 1                                                         ______________________________________                                        Outputs from                                                                           Outputs from Decoder DE1                                             Counter CO1                                                                            TB0    TB1    TB2  TB3  TB4  TB5  TB6  TB7                           ______________________________________                                        000      H      L      L    L    L    L    L    L                             001      L      H      L    L    L    L    L    L                             010      L      L      H    L    L    L    L    L                             011      L      L      L    H    L    L    L    L                             100      L      L      L    L    H    L    L    L                             101      L      L      L    L    L    H    L    L                             110      L      L      L    L    L    L    H    L                             111      L      L      L    L    L    L    L    H                             ______________________________________                                    

Terminals JA1, JA2, JA3, JA4 and JA5 of the lens adaptor shown in FIG. 2are adapted to be electrically connected with respective terminals JB1,JB2, JB3, JB4 and JB5 provided on the camera body. The terminal JA1 is aterminal to which a power line +E from the power source BA is connectedthrough the terminal JB1; the terminal JA2 is a terminal to which theclock pulses CP are fed from the camera body through the terminal JB2;the terminal JA3 is a terminal to which the start signal is suppliedfrom the camera body through the terminal JB3; the terminal JA4 is aterminal by which the ground potential is applied from the camera bodythrough the terminal JB4; and the terminal JA5 is an output terminalthrough which an output from the circuit arrangement in the lens adaptoris supplied to the camera body by way of the terminal JB5. TerminalsJL1, JL2, JL3, JL4 and JL5 of the interchangeable lens assembly shown inFIG. 3 are likewisely adapted to be connected to the mating terminalsJA1 to JA5, respectively, on the camera body. When the start signalappearing at the terminal JB3 on the camera body is supplied through theterminal JA3 or JL3, counters CO3 and CO4 and a D flip-flop DF3, allshown in FIG. 2, are released from the respective reset conditions, anda decoder DE3 and a read-only memory (ROM) RO1 are brought in acondition ready to generate a respective output. Simultaneouslytherewith, the start signal is also fed to a one-shot circuit OS4 and,consequently, flip-flops FF2 and FF3 are reset in response to a pulsefrom the one-shot circuit OS4. Similarly, in FIG. 3, counters CO5, CO6and CO7 and D flip-flops DF5 and DF6 are released from the respectivereset conditions, and a decoder DE4 and a read-only memory (ROM) RO2 arebrought in a condition ready to generate a respective output. Inaddition, in response to a pulse from a one-shot circuit OS5, flip-flopsFF4, FF5 and FF6 are reset. The counter CO3 and decoder DE3 shown inFIG. 2 as well as the counter CO5 and decoder DE4 shown in FIG. 3 are ofa construction identical with the counter CO1 and decoder DE1 shown inFIG. 1, and each of the decoders DE3 and DE4 generates a respectivepulse from their output terminals TA0 to TA7 or TL0 to TL7 in timedrelation to the pulse emerging from the output terminals TB0 to TB77 ofthe decoder DE1 whereby the circuit arrangement in the camera body andthat in the accessory are synchronized with each other.

Hereinafter, the operation of the system will be described by way ofexample with the aid of Table 2, which illustrates the relationshipbetween examples of data stored in the ROM for the storage of variousdata on the accessories at different addresses and the significancesthereof, and Table 3 which illustrates the relationship between thecoded data and the significances thereof.

                                      TABLE 2                                     __________________________________________________________________________    Address                                                                       a.sub.6                                                                         a.sub.5                                                                         a.sub.4                                                                         a.sub.3                                                                         a.sub.2                                                                         a.sub.1                                                                         a.sub.0                                                                         Significance                                                                           Data                                                                              Significance                                       __________________________________________________________________________    0 0 0 0 0 0 1 Accessory check                                                                        11100                                                  0 0 0 0 0 1 0 Accessory type                                                                         00011                                                                             Teleconverter A                                    0 0 0 0 0 1 1 Lens check                                                                             11100                                                  0 0 0 0 1 0 0 Lens Avo 10100                                                                             F 1.8                                              0 0 0 0 1 0 1 Lens Avmax                                                                             10001                                                                             F 22                                               0 0 0 0 1 1 0 Shortest focal                                                                         01100                                                                             50 mm                                                            length                                                          0 0 0 0 1 1 1 Longest focal                                                                          11111                                                                             Fixed                                                            length                                                          0 0 1 0 0 0 0 Distance 11111                                                                             ∞  Distance                                  0 0 1 0 0 0 1 Adjustment                                                                             01101                                                                             4 m      Scale Reading                             0 0 1 0 0 1 0 Shifting Amount                                                                        01001                                                                             2        On 50 mm Lens                             0 0 1 0 0 1 1          00111                                                                             1.4                                                0 0 1 0 1 0 0          00110                                                                             1.2                                                0 0 1 0 1 0 1          00101                                                                             1                                                  0 0 1 0 1 1 0          00100                                                                             0.85                                               0 0 1 0 1 1 1          00011                                                                             0.7                                                0 0 1 1 0 0 0          00010                                                                             0.6                                                0 0 1 1 0 0 1          00010                                                                             0.6                                                0 0 1 1 0 1 0          00001                                                                             0.5                                                0 0 1 1 0 1 1          00001                                                                             0.5                                                0 0 1 1 1 0 0          00001                                                                             0.5                                                0 0 1 1 1 0 1          00001                                                                             0.5                                                0 0 1 1 1 1 0          00001                                                                             0.5                                                0 0 1 1 1 1 1          0001                                                                              0.5                                                0 1 0 0 0 0 0 Stop-down                                                                              10100                                                                             1.8      F-number Reading                          0 1 0 0 0 0 1 Number   00011                                                                             2        on 50 mm Lens                             0 1 0 0 0 1 0          00100                                                                             2.5                                                0 1 0 0 0 1 1          00101                                                                             2.8                                                0 1 0 0 1 0 0          00110                                                                             3.5                                                0 1 0 0 1 0 1          00111                                                                             4                                                  0 1 0 0 1 1 0          01000                                                                             4.5                                                0 1 0 0 1 1 1          01001                                                                             5.6                                                0 1 0 1 0 0 0          01010                                                                             6.7                                                0 1 0 1 0 0 1          01011                                                                             8                                                  0 1 0 1 0 1 0          01100                                                                             9.5                                                0 1 0 1 0 1 1          01101                                                                             11                                                 0 1 0 1 1 0 0          01110                                                                             13                                                 0 1 0 1 1 0 1          01111                                                                             16                                                 0 1 0 1 1 1 0          10000                                                                             19                                                 0 1 0 1 1 1 1          10001                                                                             22                                                 0 1 1 0 0 0 0 Focal Length                                                                           01001                                                                             35 mm    Focal Length                              0 1 1 0 0 0 1 Adjustment                                                                             01010                                                                             40       Reading on                                0 1 1 0 0 1 0 Shifting Amount                                                                        01011                                                                             45       35-135 mm                                 0 1 1 0 0 1 1          01100                                                                             50       Zoom Lens                                 0 1 1 0 1 0 0          01101                                                                             55                                                 0 1 1 0 1 0 1          01110                                                                             60                                                 0 1 1 0 1 1 0          01111                                                                             70                                                 0 1 1 0 1 1 1          10000                                                                             75                                                 0 1 1 1 0 0 0          10001                                                                             85                                                 0 1 1 1 0 0 1          10010                                                                             100                                                0 1 1 1 0 1 0          10011                                                                             120                                                0 1 1 1 0 1 1          10100                                                                             135                                                1 0 0 0 0 0 0 Focal Length                                                                           00000                                                                             0        ΔAv of                              1 0 0 0 0 0 1 Adjustment                                                                             00000                                                                             0        35-135 mm                                 1 0 0 0 0 1 0 Shifting Amount                                                                        00000                                                                             0        Zoom Lens                                 1 0 0 0 0 1 1          00000                                                                             0                                                  1 0 0 0 1 0 0          00000                                                                             0                                                  1 0 0 0 1 0 1          00001                                                                             1/8                                                1 0 0 0 1 1 0          00001                                                                             1/8                                                1 0 0 0 1 1 1          00010                                                                             2/8                                                1 0 0 1 0 0 0          00010                                                                             2/8                                                1 0 0 1 0 0 1          00011                                                                             3/8                                                1 0 0 1 0 1 0          00101                                                                             6/8                                                1 0 0 1 0 1 1          01000                                                                             8/8                                                1 0 1 0 0 0 0 Focal Length                                                                           00001                                                                             1 (35 mm)                                                                              Zone on 35-135 mm                         1 0 1 0 0 0 1 Adjustment                                                                             00001                                                                             1 (40)   Zoom Lens                                 1 0 1 0 0 1 0 Shifting Amount                                                                        00001                                                                             1 (45)                                             1 0 1 0 0 1 1          00001                                                                             1 (50)                                             1 0 1 0 1 0 0          00010                                                                             2 (55)                                             1 0 1 0 1 0 1          00010                                                                             2 (60)                                             1 0 1 0 1 1 0          00010                                                                             2 (70)                                             1 0 1 0 1 1 1          00100                                                                             3 (75)                                             1 0 1 1 0 0 0          00100                                                                             3 (85)                                             1 0 1 1 0 0 1          01000                                                                             4 (100)                                            1 0 1 1 0 1 0          10000                                                                             5 (120)                                            1 0 1 1 0 1 1          10000                                                                             5 (135)                                            __________________________________________________________________________

                  TABLE 3                                                         ______________________________________                                               F-stop                                                                 Data   Num-             Focal       Type of                                   Code   ber     Distance Length                                                                              Av    Accessory                                 ______________________________________                                        0 0 0 0 0                                                                            1.2     0.5 m    below 0                                                                       8 mm                                                  0 0 0 0 1                                                                            1.4     0.6      12.5  1/8   bellows A                                 0 0 0 1 0                                                                            1.7     0.7      16    2/8   rev. adap. A                              0 0 0 1 1                                                                            2       0.85     18    3/8   teleconverter A                           0 0 1 0 0                                                                            2.5     1        20    4/8   extension ring A                          0 0 1 0 1                                                                            2.8     1.2      24    5/8                                             0 0 1 1 0                                                                            3.5     1.4      25    6/8                                             0 0 1 1 1                                                                            4       1.7      28    7/8                                             0 1 0 0 0                                                                            4.5     2        30    8/8                                             0 1 0 0 1                                                                            5.6     2.5      35    9/8   bellows M                                 0 1 0 1 0                                                                            6.7     2.8      40    10/8  rev. adap. M                              0 1 0 1 1                                                                            8       3.5      45    11/8  teleconverter M                           0 1 1 0 0                                                                            9.5     4        50    12/8  extension ring M                          0 1 1 0 1                                                                            11      4.5      55                                                    0 1 1 1 0                                                                            13      5.6      60                                                    0 1 1 1 1                                                                            16      6.7      70                                                    1 0 0 0 0                                                                            19      8        75                                                    1 0 0 0 1                                                                            22      9.5      85                                                    1 0 0 1 0                                                                            27      11       100                                                   1 0 0 1 1                                                                            32      13       120                                                   1 0 1 0 0                                                                            1.8     16       135                                                   1 0 1 0 1                                                                            1.9     19       180                                                   1 0 1 1 0                                                                            3.3     22       200                                                   1 0 1 1 1                                                                            3.6     27       250                                                   1 1 0 0 0                                                                            3.8     32       300                                                   1 1 0 0 1                                                                            4.2     40       360                                                   1 1 0 1 0                                                                            4.3     45       400                                                   1 1 0 1 1                                                                            5       54       500                                                   1 1 1 0 0                                                                            6.3     64       600                                                   1 1 1 0 1                                                                            6.5     80       800                                                   1 1 1 1 0                                                                            6.9     91       1000 or                                                                       more                                                  1 1 1 1 1      ∞  fixed                                                 ______________________________________                                    

Referring to Table 2, since the flip-flop FF2 is reset through theone-shot circuit OS4 when the start signal is outputed, the Q output ofthe D flip-flop DF3 remains in a high level state even though the Dflip-flop DF3 is released from the reset condition, and therefore, aswitching circuit AS1 remains in a conducting state. Similarly, even inthe circuit shown in FIG. 3, the Q output of the D flip-flop DF5 remainsin a low level state and a switching circuit AS2 remains in anon-conducting state. In this case, data from the lens adaptor can betransmitted to the camera body. In the first place, the counter CO4generates an output signal "01" in response to the pulse from the outputterminal TA1 of the decoder DE3, and therefore, the ROM RO1 is suppliedwith an input signal "0000001" as an address. Upon receipt of the signal"0000001" by the ROM RO1, a particular location of the ROM RO1 where acheck code "11100" for the adaptor is stored is designated and the ROMRO1 subsequently generates data "11100". On the other hand, theflip-flop FF3 is set in response to the negative edge of the clock pulseCP which emerges from an AND gate AN23 when the output terminal TA1 isin a high level state, and is reset in response to the negative edge ofthe clock pulse CP which emerges from an AND gate AN22 when the outputterminal TA2 is in a high level state. Accordingly, the Q output of theflip-flop FF3 is in a high level state during the high level state ofthe output terminal TA2, and in response to the positive edge of theclock pulse CP during this period, that is, at the time the output fromthe output terminal TA2 sets up to a high level state, the data from theROM RO1 are parallelly fed to a shift register SR2. Subsequently, insynchronism with the positive edge of the clock pulse CP applied to aninput terminal CL, the above described data are outputed serially fromthe most significant bit and are then taken in a shift register SR1,shown in FIG. 1, through the switching circuit AS1 and then through theterminals JA5 and JB5. At this time, the shift register SR1 takes in thedata from the terminal JB5 bit by bit in response to the negative edgeof the clock pulses CP. Since the data transferred from the lens adaptorare comprised of five bits, the first bit of the data fed at a timingcorresponding to the positive edge of the output from the terminal TA3is taken in the shift register SR1 in the camera body at a timingcorresponding to the negative edge of the clock pulse CP during the highlevel state of the output from the output terminal TB3 and, thereafter,the succeeding bits are fed one by one at different timingscorresponding to the positive edges of the respective outputs from theoutput terminals TA4, TA5, TA6 and TA7. In this way, the read-inoperation of one data completes in response to the negative edge of theclock pulse during the high level state of the output from the outputterminal TB7 and output data from the shift register SR1 are parallellylatched in a register REG1 at a timing corresponding to the positiveedge of the output subsequently emerging from the output terminal TB0.Inputs and outputs of a decoder DE1 in the camera body have therelationship as tabulated in Table 4 below.

                  TABLE 4                                                         ______________________________________                                        Outputs                                                                       from                                                                          Counter                                                                              Outputs from Decoder DE2                                               CO2    d0    d1    d2  d3  d4  d5  d6  d7  d8  d9  d10                                                    d11                                               ______________________________________                                        0 0 0 0                                                                              L     L     L   L   L   L   L   L   L   L   L                                                      L                                                                             0 0 0 1 H L L L L L L L L L L L                                               0 0 1 0 L H L L L L L L L L L L                                               0 0 1 1 L L H L L L L L L L L L                                               0 1 0 0 L L L H L L L L L L L L                                               0 1 0 1 L L L L H L L L L L L L                                               0 1 1 0 L L L L L H L L L L L L                                               0 1 1 1 L L L L L L H L L L L L                                               1 0 0 0 L L L L L L L H L L L L                                               1 0 0 1 L L L L L L L L H L L L                                               1 0 1 0 L L L L L L L L L H L L                                               1 0 1 1 L L L L L L L L L L H L                                               1 1 0 0 L L L L L L L L L L L H                   ______________________________________                                    

The counter CO2 having its output terminals connected to input terminalsof the decoder DE2 is incremented by one in response to the positiveedge of each pulse from the output terminal TB7. On the other hand, atthe time the initial data, that is, the check data are latched in theregister REG1 at a timing corresponding to the positive edge of thepulse from the output terminal TB0, the output terminal d0 of thedecoder DE2 is in a high level state. Accordingly, the positive edge ofthe pulse from the output terminal TB1 is applied to a latch terminal ofthe register REG2 through an AND gate AN3 so that the data from theregister REG1 can be latched in this register REG2. An output signalfrom the register REG2 is discriminated by an AND gate AN15 as towhether or not it is "11100", and when it is "11100" in view of the factthat the lens adaptor is coupled to the camera body, the AND gate AN15generates a high level signal, whereas when the lens adaptor is notcoupled to the camera body, the AND gate AN15 generates a low levelsignal. The output from this AND gate AN15 is in turn fed to, forexample, a display unit (not shown) so designed as to indicate thepresence or absence of the lens adaptor.

In FIG. 2 the counter CO4 generates an output signal "10" in response tothe positive edge of the pulse emerging from the output terminal TA1 andthe address "0000010" of the ROM RO1 is specified. As a result of this,data indicative of the type of the lens adaptor are outputed from theROM RO1 as shown in Table 2. These data are fixed, so that as shown inTable 3, an automatic bellows of a type having a capability oftransmitting a physical aperture control information between the camerabody and the lens assembly is represented by "00001" and an automaticreverse adaptor of a type having a capability of transmitting a physicalaperture control information between the camera body and the lensassembly is represented by "00010". These data are also latched, in amanner similar to that described above, in the register REG1 in thecamera body at a timing at which the output terminal TB0 is rendered ina high level state, and at this time, the counter CO2 generates anoutput "0010". In response to the signal "0010" from the counter C02,the output terminal d1 of the decoder DE2 is rendered in a high levelstate and, accordingly, the data fed from the register REG1 are latchedin the register REG3.

When the counter CO4 generates an output "10", the one-shot circuit OS3generates a high level signal which is in turn supplied to the flip-flopFF2 to set the latter. Subsequently, at the timing corresponding to thepositive edge of the high level output at the terminal TA0, (It is to benoted that at this time transfer of the data indicative of the type ofthe lens adaptor have already been completed.), a low level signal isfed from the Q output terminal of the flip-flop FF2 to the D inputterminal of the D flip-flop DF3, thereby bringing the switching circuitAS1 into a non-conductive state to cease the transfer of the data fromthe lens adaptor.

In a manner similar to the counter CO2 shown in FIG. 2, the counter CO3shown in FIG. 3 also counts the positive edge of the high level pulse atthe output terminal TL1 and, when the count output becomes "010", an ANDgate AN25 generates a high level signal which is applied to a one-shotcircuit OS6 to cause the latter to generate, in response to the positiveedge of the high level signal from the AND gate AN25, a high level pulsewith which the flip-flop FF4 is set. As is the case with the D flip-flopDF3 shown in FIG. 2, the Q output from the D flip-flop DF5 is brought ina high level state in response to the positive edge of the high levelsignal at the output terminal TL0 and, therefore, the switching circuitAS2 is brought into a conductive state thereby enabling the transfer ofthe data from the interchangeable lens assembly. At the positive edge ofthe subsequent high level signal at the output terminal TL1, the counterCO6 generates an output signal "011". This three bit signal from thecounter CO6 is given to the least significant three bits of the inputsb1 of a multiplexer MP2. Since the Q output from the D flip-flop DF6 isstill in a low level state, the multiplexer MP2 generates data "0000011"from its input b1, which data become an address signal to be fed to theROM RO2. Then, as shown in Table 2, the data "11100" for checkingpurpose are outputed from the ROM RO2 and are read in the register REG4shown in FIG. 1 in a manner similar to that described hereinbefore. Itis to be noted that AND gates AN28 and AN29, an OR gate OR4, theflip-flop FF6 and a shift register SR3, shown in FIG. 3, are of acircuit construction similar to AND gates AN23 and AN24, an OR gate OR3,the flip-flop FF3 and the shift register SR2, show in FIG. 2,respectively.

The data which have been read in the register REG4 are checked by an ANDgate AN16 as to whether or not they are "11100". If they are not found"11100", this means that the interchangeable lens assembly has not beencoupled to the camera body, and in such case the AND gate AN16 generatesa low level signal and an AND gate AN17 is then enabled to allow thepassage of the pulse from the output terminal TB2 therethrough in theform of a read-in completion signal end1. Thereafter, in response to thepositive edge of each high level pulse appearing at the output terminalTL1, the counter CO6 successively generates output signals "100", "101","110" and "111" and, accordingly, address data "0000100", "0000101","0000110" and "0000111" are successively outputed from the multiplexerMP2. As shown in Table 2, pieces of information of the interchangeablelens assembly including the minimum available F-number Avo, the maximumavailable F-number Avmax, the shortest focal length and the longestfocal length are stored at the above described addresses of the ROM RO2.Referring to Table 3, the data on the F-number are defined such that theordinarily utilized F-numbers within the range of F-1.2 to F-32 andspaced at intervals of 0.5 Ev are represented by "00000" to "10011"whereas the F-numbers within the range of F1.8 to F6.9, which are notspaced at interval of 0.5 Ev, but which represent the minimum availableF-number of a certain lens assembly, are represented by "10100" to"11110". On the other hand, with respect to the data on the focallength, the focal length is classified into not longer than 8 mm, 12.5mm, 16 mm, . . . 800 mm and not shorter than 1000 mm as shown in Table3, which are respectively represented by "00000", "00001", . . . "11101"and "11110". In addition, at the addresses "0000110" and "0000111", theshortest and longest focal lengths of a zoom lens assembly are stored.In the case of an interchangeable lens assembly of a fixed focal length,the data on the above described focal length and the data " 11111"indicative of the fixed focal length are stored respectively at theaddresses "0000110" and "0000111". Accordingly, in response to thesuccessive generation of the above described address data "0000100" to"0000111" from the multiplexer MP2, such pieces of information of theinterchangeable lens assembly including the minimum available F-number,the maximum available F-number, the shortest focal length and thelongest focal length are successively stored in the registers REG5,REG6, REG7 and REG8 in the camera body, respectively. An AND gate AN18serves to determine whether or not the output from the register REG8 inwhich the data of the longest focal length have been read is "11111",and in the case where the focal length of the interchangeable lensassembly is fixed, a high level pulse emerges from the AND gate AN18.The output terminal of the AND gate AN18 is so connected to the D inputterminal of a D flip-flop DF2 that the output from the gate AN18 can betaken in the D flip-flop DF2 in response to the positive edge of thepulse from the output terminal TB2 of the decoder DE1 when the outputfrom the output terminal d6 of the decoder DE2 is in a high level state.

Referring to FIG. 3, when the counter CO6 outputs "111", a high levelsignal emerges from an AND gate AN26 and, in response to the positiveedge of the high level signal from the gate AN26, a one-shot circuit OS7generates a high level pulse. In response to this high level pulse, theflip-flop FF5 is set, and the Q output of the D flip-flop DF6 is broughtinto a high level state in response to the positive edge of the highlevel pulse subsequently fed from the output terminal TL0. Then, an ANDgate AN27 is enabled to allow the passage of pulses from the outputterminal TL1 therethrough to the counter CO7 on the one hand and toallow the multiplexer MP2 to output such data as have been fed to theinput terminals b2. When the Q output from the D flip-flop DF6 isbrought into the high level state and the pulse from the output terminalTL1 is subsequently fed to the counter CO7, the counter CO7 outputs"001" and a multiplexer MP1 outputs such data as have been fed to inputterminals d1 thereof from a block 10. This block, 10 generates the datacorresponding to the displacement of a focusing ring, which is adistance setting member of the interchangeable lens assembly, from theinfinity (∞) position. These data are adapted to output four bit datastarting from "0000" irrespective of the type of the interchangeablelens assembly. Since these data are applied to the least significantfour bits of the input terminals b2 of the multiplexer MP2 and since theoutput from the counter CO7 is applied to the most significant threebits of the input terminals b2 of the multiplexer MP2, one of theaddress data "0010000" to "0011111" is outputed from the multiplexer MP2and is then fed to the ROM RO2. IN a territory of the ROM RO2 specifiedby the addresses "0010000" to "0011111", as shown in Table 2, dataconcerning the focusing distance corresponding to the displacement fromthe infinity position of the distance setting member of theinterchangeable lens assembly are stored. Accordingly, these data areread in the register REG9 in the camera body.

When the output of the counter CO7 subsequently becomes "010", themultiplexer MP1 outputs such data as have been fed to the inputterminals a2 thereof from a block 11. This block 11 generates the datacorresponding to the number of the positions of an aperture adjustingring stopped down from the minimum available F-number, which apertureadjusting ring constitutes an aperture setting member of theinterchangeable lens assembly. These data are adapted to output four bitdata starting from "0000" irrespective of the type of theinterchangeable lens assembly. It is, however, to be noted that, in thecase of the interchangeable lens assembly having a fixed aperture (forexample, a tele-photo lens assembly of mirror reflex type), only thedata "0000" are outputed. From the multiplexer MP2, one of the data"0100000" to "0101111" is outputed and is then fed to the ROM RO2. In aterritory of the ROM RO2 specified by the addresses "0100000" to"0101111", as shown in Table 2, data concerning the aperture valuescorresponding to the number of the positions of the aperture adjustingrings which can be stopped down from the minimum available F-number areprovided. Accordingly, the data of the preset aperture value outputedfrom the ROM RO2 are read in the register REG10 in the camera body.

Referring to FIG. 1, when the Q output of the D flip-flop DF2 is in ahigh level state at the time the data of the preset aperture value areread in the register REG10, that is, when it is determined that theinterchangeable lens assembly coupled to the camera body is the one offixed focal length, an AND gate AN20 is enabled to allow the passagetherethrough of the pulse from the output terminal TB2 which emergesfrom the AND gate AN20 as a read-in completion signal end2, therebycompleting the read-in operation. This is because, since thesubsequently read-in data are all related to the data on the zoom lensassembly, no read-in operation is required in the case of the lensassembly of a fixed focal length.

Referring to FIG. 3, when the counter CO7 generates an output "011", themultiplexer MP1 outputs such data as have been supplied to the inputterminals a3 from a block 12. This block 12 generates the displacementof a zooming ring from the position of the shortest focal length, whichzooming ring constitutes a focal length setting member of the zoom lensassembly, and outputs four bit data starting from "0000" as is the casewith the blocks 10 and 11. From the multiplexer MP2, one of the data"0110000" to "0111111" from the input terminals b2 is outputed and fedto the ROM RO2. At a territory of the ROM RO2 specified by the addresses"0110000" to "0111111", as shown in Table 2, the data of the presetfocal lengths corresponding to the positions of the focal length settingmember are stored, and these data are outputed from the ROM RO2 and thenread in the register REG11 in the camera body.

When the counter CO7 subsequently generates an output "100", themultiplexer MP1 outputs the same data as have been supplied to the inputterminals a3, and one of the data "1000000" to "1001111" is fed to theROM RO2. At a territory of the ROM RO2 specified by the addresses"1000000" to "1001111", as shown in FIG. 2 the data ΔAv of the amount ofchange in aperture value resulting from the change of the focal lengthof the zoom lens assembly are stored and, when outputed from the ROMRO2, are read in the register REG12 in the camera body.

In the event that the counter CO7 comes to generate an output "101", themultiplexer MP1 generates the same data as have been supplied to theinput terminals a3 thereof from the block 12, and one of the data"1010000" to "1011111" is fed to the ROM RO2. At a territory of the ROMRO2 specified by these data, the data indicating where the preset focallength f of the zoom lens assembly lies between the shortest focallength f min and the longest focal length f max are stored in terms ofthe percentage showing the position of the preset focal length f spacedfrom the shortest focal length f min, which percentage is expressed bythe following equation: ##EQU1## More specifically, if the percentagefalls within 0 to 19%, the output from the ROM RO2 will be "00001" whichmeans that the preset focal length of the zoom lens lies in a firstzone; if it falls within the range of 20 to 39%, the output will be"00010" which means that the preset focal length lies in a second zone;if it falls within the range of 40 to 59%, the output will be "00100"which means that the preset focal length lies in a third zone; if itfalls within the range of 60 to 79%, the output will be "01000" whichmeans that the preset focal length lies in a fourth zone; and if itfalls within the range of 80 to 100%, the output will be "10000" whichmeans that the preset focal length lies in a fifth zone.

At the same time as the data indicative of the above described zones areread in the register REG13 in the camera body, a read-in completionsignal end3 emerges from an AND gate AN21 and the read-in completionsignal end emerges from the OR gate OR3. This read-in completion signalend, which is hereinafter referred to as "end signal", is appliedthrough an OR gate OR2 to the flip-flop FF1 to reset the latter.Accordingly, the read-in start terminal start of an AND gate AN40 isrendered in a low level state with the counters CO1 and CO2 and the Dflip-flop DF2 consequently reset. Accordingly, the decoder DE1 ceasesgenerating the timing signal. Similarly, the counters CO3 and CO4 andthe D flip-flop DF3, shown in FIG. 2 are reset while the decoder DE3 andthe ROM RO1 cease generating their respective outputs. Moreover, thecounters CO5, CO6 and CO7 and the D flip-flops DF5 and DF6, shown inFIG. 3 are reset while the decoder DE4 and the ROM RO2 cease generatingtheir respective outputs. In this way, the read-in operation is broughtto end.

Referring to FIG. 1, where the light measuring switch S1 remains closedat the time of completion of the read-in operation, the D flip-flop DF1continues generating a high level signal from the Q output terminalthereof and, therefore, the clock pulses continue to be fed through theAND gate AN1 to the divider DI1 which in turn generate clock pulses of 4Hz. In response to this 4 Hz clock pulses, a high level pulse emergesfrom the one-shot circuit OS2, which is in turn applied through the ORgate OR1 to the flip-flop FF1 to cause the latter to be again reset torender the Q output of the flip-flop FF1 in a high level state, therebygenerating the start signal. Thus, so long as the light measuring switchS1 remains closed, the data from the lens adaptor and theinterchangeable lens assembly are repeatedly read in at a cycle of 4 Hz.

Although the shift registers SR2 and SR3 have been described as operableto parallelly take in the data from the ROMs RO1 and RO2 when the outputterminals TA7 and TB7 are in a high level state, respectively, and tosupply bit by bit these data to the camera body in response to thepositive edges of the high level pulses at the output terminals TA0 andTL0, respectively, a specific construction of each of these shiftregisters is such as follows. Namely, each of the shift registers SR2and SR3 is so constructed that there is provided a flip-flop, to whichthe data of each of the bits parallelly fed thereto are preset, for eachbit, an output terminal of the flip-flop corresponding to the leastsignificant bit being to connected to an input terminal of the flip-flopcorresponding to the next least significant bit that the data preset ineach of the flip-flops can be sequentially shifted from the leastsignificant bit to the most significant bit in synchronism with theclock pulses. In addition, separately of the above described flip-flops,another flip-flop is employed with its input terminal so connected tothe output terminal of the flip-flop corresponding to the mostsignificant bit that the above described data taken in can be, afterhaving been delayed a time corresponding to one clock pulse, outputedfrom such another flip-flop.

In the foregoing description, the start signal has been described asoutputed from the flip-flop FF1 upon closure of the light measuringswitch S1. However, an alternative method is possible. Namely, a currentflowing through the power line +V activated upon closure of the switchS1 may be used as the start signal and, in this case, the start signalmay be transmitted to the accessory through the terminal JB1. It is tobe noted that the timing at which the start signal is generated may notbe limited to the timing at which the light measuring switch S1 isclosed, but may be at any time prior to the time at which thephotographic exposure takes place in the camera system. It is also to benoted that, although the circuit arrangement according to this inventionhas been shown and described as constituted by a logic circuit in theforegoing embodiment, it may be substituted by a so-calledmicroprocessor (CPU) so that the operation can sequentially becontrolled.

Hereinafter, one of the setting members which have schematically beenshown in the form of the respective blocks 10, 11 and 12 in FIG. 3, forexample, the aperture adjusting ring, will be described in detail withreference to FIG. 4.

FIG. 4 illustrates a circuit diagram showing the construction of thesetting member. Referring to FIG. 4, a slide VT can be moved togetherwith the aperture adjusting ring 13 provided on the lens assembly to anyone of the click positions shown respectively by (1) to (16) andcorresponding to the associated positions of the aperture adjusting ring13. A patterned conductive strip CT is electrically grounded while theother patterned conductive strips PA0, PA1, PA2 and PA3 are connected tothe power line +E through respective resistors. Accordingly, dependingon the position of the slide VT, some or all of the conductive stripsPA0 to PA3 are selectively short circuited through the slide VT to theconductive strip CT and, therefore, some or all of the inverters IN20 toIN23 connected with the conductive strips PA0 to PA3, respectively,selectively generate a high level output. Where the slide VT is held inposition clear from any one of the conductive strips PA0 to PA23, all ofthe inverters IN20 to IN23 generate a low level output. The inverterIN23 is in turn connected to an output d3 and also to one of the inputterminals of an exclusive OR gate EO2. The inverter IN22 is in turnconnected to the other of the input terminals of the exclusive OR gateEO2 having its output connected to an output terminal d2 and also to oneof the input terminals of an exclusive OR gate EO1. The inverter IN21 isin turn connected to the other of the input terminals of the exclusiveOR gate EO1 having its output connected to an output terminal d1 andalso to one of the input terminals of an exclusive OR gate EO0. Theinverter IN20 is in turn connected to the other of the input terminalsof the exclusive OR gate EO0 having its output connected to an outputterminal d0.

The conductive strips PA0 to PA3 are gray-coded, and the relationshipbetween the inputs to the inverters IN20 to IN23 and the outputs at therespective output terminals d0 to d3 depending on the position of theslide VT according to the code is tabulated in Table 5 together with thestep-down number at each position of the slide VT.

                  TABLE 5                                                         ______________________________________                                        Inputs             Outputs     Stop-down                                      Position                                                                             IN23   IN22   IN21 IN20 d3  d2  d1  d0  Number                         ______________________________________                                        (1)    0      0      0    0    0   0   0   0   0                              (2)    0      0      0    1    0   0   0   1   0.5                            (3)    0      0      1    1    0   0   1   0   1                              (4)    0      0      1    0    0   0   1   1   1.5                            (5)    0      1      1    0    0   1   0   0   2                              (6)    0      1      1    1    0   1   0   1   2.5                            (7)    0      1      0    1    0   1   1   0   3                              (8)    0      1      0    0    0   1   1   1   3.5                            (9)    1      1      0    0    1   0   0   0   4                              (10)   1      1      0    1    1   0   0   1   4.5                            (11)   1      1      1    1    1   0   1   0   5                              (12)   1      1      1    0    1   0   1   1   5.5                            (13)   1      0      1    0    1   1   0   0   6                              (14)   1      0      1    1    1   1   0   1   6.5                            (15)   1      0      0    1    1   1   1   0   7                              (16)   1      0      0    0    1   1   1   1   7.5                            ______________________________________                                    

Hereinafter, the relationship between the preset F-number and theselected position of the slide VT will be described. In the case of thelens assembly having an F-number range of F1.2 to F16, if the apertureadjusting ring is set at F1.2 (Av=0.5), the slide VT is held at theposition (1) and the data "0000" indicating that the stop-down number iszero are outputed from the output terminals d3 to d0. On the other hand,if it is set at F1.4 (Av=1), the slide VT is held at the position (2)and the data "0001" indicating that the stop-down number is 0.5 areoutputed from the output terminals d3 to d0. Similarly, if it is set atF13 (Av=7.5), the data "1110" indicating that the stop-down number is 7are outputed from the output terminals d3 to d0 and, if it is set atF16, the data "1111" indicating that the stop-down number is 7.5 areoutputed from the output terminals d3 to d0.

FIG. 5 illustrates a block circuit diagram showing the exposure controlunit for effecting an exposure control on the basis of the data read inthe camera body. In the circuit arrangement shown in FIG. 5, both acountermeasure against the possibility that the interchangeable lensassembly has not been coupled to the camera body or the interchangeablelens assembly is of a type having no automatic aperture settingmechanism and a countermeasure against any possible change of theeffective aperture (i.e., reduction of the preset aperture) resultingfrom the use of the lens adaptor are taken.

Referring to FIG. 5, a light measuring circuit 20 is adapted to receivean output signal from a photosensor PD which measure the amount of lightreflected from a target object to be photographed and then impingingthereupon through the lens assembly, and an output from the circuit 20is subjected to an analog-to-digital conversion in an A-D converter 22.Assuming that the brightness of the object to be photographed isexpressed by Bv, the minimum F-number is expressed by Avo, the amount ofchange of the aperture resulting from the use of the lens adaptor isexpressed by k, and the restricted aperture, that is, the aperture whichhas been restricted by the use of the lens adaptor because the bore sizeof the lens adaptor is limited, is expressed by Avc, the above describedoutput will represent the difference Bv-(Avo+k) if Avo+k>Avc or Bv-Avcif Avo+k≦Avc. Where the lens adaptor of a type having no capability oftransmitting aperture information between the lens assembly and thecamera body is used or where the interchangeable lens assembly has notbeen coupled to the camera body, the above described output willrepresent the difference Bv-Avn, wherein Avn corresponds to the actualaperture value given when the lens assembly has been stopped down or theaperture value when the lens assembly has not been coupled to the camerabody. Where only the lens assembly is used, i.e., coupled to the camerabody, it will represent the difference Bv-Avo.

The relationship between Avo+k and Avc will be described in detail. Byway of example, assuming that a tele-converter is coupled as the lensadaptor to the lens assembly having an F-number range of F1.4(Avo=1) toF16 (Avmax=8) and the effective aperture of the lens assembly isaccordingly stopped down one position, the effective F-number range willbe F2 (Av=2) to F22 (Av=9). In the event that the minimum F-number ofthe lens assembly is restricted to, for example, F4 (Av=4) because ofthe tele-converter having been coupled to such a lens assembly, theeffective F-number range of the lens system including the lens assemblyand the tele-converter will be F4 to F22 and the F-number range fromF1.4 to F4 (1≦Av<4) can no longer be utilized. Similarly, where the lensassembly having the F-number range from F3.5 (Avo=3.5) to F22 (Avmax=9)is used in combination with the above described tele-converter, theeffective F-number range of the lens system is F4.5 (Av=4.5) to F32(Av=10) and, since the restricted aperture value resulting from the useof the tele-converter is F4 (Av=4), the whole F-number range of the lensassembly can be effectively utilized.

Reference numeral 24 represents a data output device from which data Svof the preset film speed is outputed, and an adder 26 performs one ofthe following calculations based on the data fed from both the A-Dconverter 22 and the data output device 24:

    Bv-(Avo+k)+Sv=Ev-(Avo+k)

    Bv-Avc+Sv=Ev-Avc

    Bv-Avn+Sv=Ev-Avn

    Bv-Avo+Sv=Ev-Avo

The data calculated in the adder 26 is fed to both an exposurearithmetic circuit 40 and a multiplexer 42.

The exposure arithmetic circuit 40 also receives the data from decoders28, 30, 32 and 34. The decoder 28 is operable to convert the data of theminimum F-number of the lens assembly fed from the register REG5(FIG. 1) into processable data Avo which are in turn outputed to theexposure arithmetic circuit 40. The decoder 30 is operable to feed thedata Avc of the restricted aperture resulting from the use of theaccessory, based on the data of the type of the accessory fed from theregister REG3, to the circuit 40. The decoder 32 is operable to feed tothe circuit 40, the data k of the amount of change of the aperture as aresult of the use of the accessory based on the type of the accessoryfed from the register REG3. The decoder 34 is operable to convert thedata of the preset aperture value fed from the register REG10 (FIG. 1)into processable data Avs which are in turn outputed to the circuit 40.Reference numeral 36 represents a data output device for outputting dataTvs of a preset exposure time to the circuit 40. Reference numeral 38represents a mode setting device having a plurality of output terminalsall connected to the exposure arithmetic circuit 40. This mode settingdevice 38 is operable in such a manner that, in the case of the shutterspeed priority mode (hereinafter referred to as "T-priority mode") inwhich the aperture of the lens assembly can automatically controlledaccording to the preset exposure time, the preset film speed and thebrightness of the target object, the output terminal T is rendered in ahigh level state; in the case of the aperture priority mode (hereinafterreferred to as "A-priority mode") in which the exposure time can beautomatically controlled according to the preset aperture value(F-number), the preset film speed and the brightness of the targetobject, the output terminal A is rendered in a high level state; in thecase of the programed control mode (hereinafter referred to as "P-mode")in which both the exposure time and the aperture can automatically becontrolled according to the preset film speed and the brightness of thetarget object, the output terminal P is rendered in a high level state;and in the case of the manual control mode (hereinafter referred to as"M-mode") in which both the exposure time and the aperture can manuallybe controlled, the output terminal M is rendered in a high level state.Since these output terminals T, A, P and M are connected to the exposurearithmetic circuit 40, the exposure arithmetic circuit 40 performs anarithmetic calculation under one of the modes assigned by one of themode designating signals which has been fed from the mode setting device38. This circuit 40 has three output terminals OUT1, OUT2 and OUT3. Theoutput terminal OUT1 feeds the data for the aperture control to anaperture control device 54, the output terminal OUT2 feeds the data forthe aperture display to an aperture display device 56, and the outputterminal OUT3 feeds the data for the exposure time control and theexposure time display to an exposure time control device 50 and anexposure time display device 52, respectively, through the multiplexer42.

Hereinafter, the arithmetic calculation performed by the exposurearithmetic circuit 40 according to the different modes will be describedwith particular reference to the flow chart shown in FIG. 6.

Referring now to FIG. 6, particularly to FIG. 6(a), at the step #1, theminimum aperture value Avo+k based on the change in aperture resultingfrom the use of the lens adaptor is compared with the restrictedaperture value Avc resulting from the use of the lens adaptor. IfAvo+k≧Avc, the process proceeds to the step #, but if Avo+k≦Avc, theprocess proceeds to the step #38 shown in FIG. 6(b). Where the processproceeds to the step #2, the data fed from the adder 26 to thearithmetic circuit 40 represent Ev-(Avo+k) and, therefore, the equation,Ev-(Avo+k)+(Avo+k)=Ev, is calculated at the step #2 to give an exposurevalue Ev which is not affected by the minimum aperture value Avo+k.

At the subsequent step #3, the mode discrimination is carried outdepending on which one of the mode designating signals is fed from themode setting device 38 through the corresponding output terminal T, A, Por M. The process proceeds to the step #4 in the case of the T-prioritymode; to the step #14 in the case of the A-priority mode; to the step#24 (FIG. 6(b)) in the case of the P-mode; and to the step #34 (FIG.6(b)) in the case of the M-mode.

Assuming that the mode designating signal is fed through the outputterminal T from the mode setting device 38, the equation, Ev-Tvs=Ave, iscalculated at the step #4 and, then, the effective aperture value Ave iscompared with Avo+k and Avmax+k at the step #5. If Avo+k≦Ave≦Avmax+k, itis possible to control to the effective aperture value Ave, and at thestep #6, the stop-down number, that is, (Ave-k)-Avo, is calculated and,thereafter, the data indicative of the stop-down number are outputed tothe output terminal OUT1. These data are fed to the aperture controldevice 54. When the aperture is stopped down according to this value,although the aperture value is Ave-k when only the lens assembly isused, the effective aperture value is Ave becomes the use of the lensadaptor results in the aperture being stopped down by k. In addition,the data Ave of the effective aperture value calculated at the step #4is output to the output terminal OUT2 at the step #7, which in turn isdisplayed through the aperture display device 56. At the step #8, thedata Tvs of the preset exposure time is outputed to the output terminalOUT3. The process then returns to the step #1 to complete a cycle whichis repeated until the shutter release is performed.

However, if Ave<Avo+k is found at the step #5, since it is not possibleto control the aperture to the effective aperture value Ave, theA-priority mode is initiated at the step #14, using the data of Avo asthe data of the preset aperture value. Moreover, even if Ave>Avmax+k isfound at the step #5, it is not possible to control the aperture and,therefore, the A-priority mode is initiated at the step #14, using Avmaxas the preset aperture value.

It is to be noted that, if the exposure time determined on the basis ofthe value Avo or Avmax which is newly determined when the Ave<Avo+k orAve>Avmax+k has been found does not fall within the controllableexposure time range of Tv=Tvmin (the shortest exposure time) to Tv=Tvmax(the longest exposure time), any photo-taking at a proper exposure canno longer be carried out. In such case, it is desirable to cause theexposure control to take place using the effective aperture value ofAvo+k and the exposure time of Tvmax and then to carry out a warning toinform the photographer of an under-exposure condition or to cause theexposure control to take place using the effective aperture value ofAvmax+k and the exposure time of Tvmax and then to carry out a warningto inform the photographer of an over-exposure condition.

The A-priority mode will now be described. At the step #14, theequation, Ev-(Avs+k)=Tv, is calculated. Avs+K represents, ashereinbefore described, the effective aperture value obtained when theaperture of the lens assembly has been controlled to Avs. At thesubsequent step #15, the data Tv of the exposure time so calculated isdiscriminated as to whether it falls within the controllable range and,if Tvmin≦Tv≦Tvmax, the data indicative of the stop-down numberrepresented by Avs-Avo are fed from the output terminal OUT1 to theaperture control device 54, the data indicative of the effectiveaperture value represented by Avs+k are fed from the output terminalOUT2 to the aperture display device 56 and the data Tv indicative of theexposure time are fed to both of the exposure time control device 50 andthe exposure time display device 52. Thereafter, the process returns tothe step #1. On the other hand, if Tv>Tvmax has been found at the step#15, the T-priority mode is initiated using Tvmax as the preset value.Even in this case, if Avs=Avmax is determined, it is desirable to carryout a warning informing the photographer of an over-exposure conditionwhile the exposure is controlled on the basis of Avmax and Tvmax.

The P-mode starting from the step #24 will now be described withparticular reference to FIG. 6(b). At the step #24, the followingcalculations are performed:

    P·Ev=Ave (0<P<1)

    Ev-Ave=Tv

and, subsequently, the value Ave is discriminated as to whether or notit falls within the controllable range. If Avo+k≦Ave≦Avmax+k, the dataof the stop-down number represented by (Ave-k)-Avo is outputed to theoutput terminal OUT1. As is the case with that during the T-prioritymode, these data represent the stop-down number by which the aperture inthe lens assembly should be stopped down, since they are the effectiveaperture value Ave so calculated. Thereafter, the data Ave of theeffective aperture value and the data of the calculated exposure timeare respectively fed to the output terminals OUT2 and OUT3 and theprocess returns to the step #1. Where Ave<Avo+k, Avo is set as the dataof the preset aperture value at the step #30 and the A-priority mode isinitiated starting from the step #14. Conversely, where Ave>Avmax+k,Avmax is set as the data of the preset exposure time and the A-prioritymode is initiated starting from the step #14.

In the case of the M-mode, the data Avs-Avo of the stop-down numberbased on the preset aperture value Avs, the effective aperture valueAvs+k, and the data Tvs of the preset exposure time are respectivelyoutputed to the output terminals OUT1, OUT2 and OUT3 and the processthen returns to the step #1.

Where Avo+k≦Avc has been determined at the step #1, since the data fedfrom the adder 26 to the arithmetic circuit 40 at this time representEv-Avc, the following equation is calculated at the step #38:

    (Ev-Avc)+Avc=Ev

At the subsequent step #39, the exposure control mode is discriminated.

In the case of the T-priority mode, Ev-Tvs=Ave is calculated at the step#40 and, then, Ave is discriminated as to whether or not it falls withinthe controllable range. If Avc≦Ave≦Avmax+k, the data of (Ave-k)-Avo, Aveand Tvs are respectively outputed to the output terminals OUT1, OUT2 andOUT3 in a manner similar to the previously described T-priority mode andthe process then returns to the step #1. If Ave<Avc, the A-priority modestarting from the step #61 is initiated using Avc-k as the presetaperture value. It is, however, to be noted that, since a properexposure can not be obtained when Tvs=Tvmin at this time, it isdesirable to effect a warning to in form the photographer of anunder-exposure condition and to effect the exposure control using Avc-kand Tvmin as the respective preset values. On the other hand, ifAve>Avmax+k, the A-priority mode starting from the step #51 is initiatedusing Avmax as the preset aperture value. Even in this case, ifTvs=Tvmax, it is desirable to effect a warning to inform thephotographer of an over-exposure condition and to effect the exposurecontrol using Avmax and Tvmax as the respective preset values.

Referring particularly to FIG. 6(c), the operation under the A-prioritymode starting from the step #50 will now be described. If Avs+k≦Avc isdetermined at the step #50, Ev-(Avs+k)=Tv is calculated and, then, Tv isdiscriminated as to whether or not it falls within the controllablerange. Where Tvmin≦Tv≦Tvmax, the data of Avs-Avo, Avs+k, and Tv arerespectively outputed to the output terminals OUT1, OUT2 and OUT3 andthe process then returns to the step #1. Where Tv<Tvmin, the T-prioritymode starting from the step #40 is initiated using Tvmin as the presetexposure time, whereas where Tv>Tvmax, the T-priority mode starting fromthe step #40 is initiated using Tvmax as the preset exposure time. Itis, however, desirable to effect a warning to inform the photographer ofan over-exposure condition and to effect the exposure control at Avmaxand Tvmax, if Avs=Avmax.

Where Avs+k<Avc is found at the step #50, the process starts form thestep #61. In this case, since the effective aperture value determined bythe preset aperture value of the lens assembly is smaller than therestricted aperture value resulting from the use of the lens adaptor,the actual effective aperture value will be Avc. At this time, Avc isset as the effective aperture value and, then, Ev-Avc=Tv is calculated.Thereafter, Tv is discriminated as to whether or not it falls within thecontrollable range. Where Tvmin≦Tv≦Tvmax, the process proceeds to thestep #64 and the data indicating that the stop-down number is zero, thedata of the effective aperture value Avc, and the data Tv of theexposure time are respectively outputed to the output terminals OUT1,OUT2 and OUT3. Thereafter, the process returns to the step #1. However,where Tv<Tvmin, since the preset effective aperture value is the minimumaperture value Avc, a proper exposure cannot be obtained and, in suchcase, after Tvmin is set as the calculated value at the step #63, theprocess proceeds to the step #64. Even in this case, it is desirable toeffect a warning to inform the photographer of an under-exposurecondition. On the other hand, where Tv>Tvmax, the T-priority modestarting from the step #40 is initiated using Tvmax as the preset value.

In the case of the P-mode, the following equations are calculated at thestep #70:

    P·Ev=Ave

    Ev-Ave=Tv

Thereafter, the process proceeds in a manner similar to that during theT-priority mode starting from the step #40.

In the case of the M-mode, if Avs+k≧Avc is found at the step #80, theprocess starting from the step #81 is performed and the data of thestop-down number Avs-Avo, the effective aperture value Avs+k, and theexposure time Tvs are respectively outputed to the output terminalsOUT1, OUT2 and OUT3. Thereafter, the process returns to the step #1.However, where Avs+k<Avc, the process proceeds from the step #80 to thestep #85 and the data of the stop-down number being zero, the effectiveaperture value Avc and the exposure time Tvs are outputed respectivelyto the output terminals OUT1, OUT2 and OUT3. Thereafter, the processreturns to the step #1.

It is to be noted that, where only the interchangeable lens assembly ismounted on the camera body, the output from the register REG3 shown inFIG. 1 is "00000" and the data of the light measured represent Bv-Avo.In such case, the ordinary arithmetic operation shown and described withreference to the flow chart of FIG. 6 can be performed if an arrangementis made to enable the decoders 30 and 32 to output the respective dataof Avc=0 and k=0.

Referring back to FIG. 5, a decoder 44 is operable on the basis of thedata of the type of the lens adaptor fed from the register REG3 todetermine whether or not the lens adaptor is of an auto-aperture controltype having a capability of transmitting physical aperture controlinformation between the camera body and the lens assembly therethrough.When the data "01001", "01010", "01011" and "01100" as shown in Table 3indicating that the accessory is not of the auto-aperture control typeare fed to the decoder 44, the output from the decoder 44 is rendered ina high level state. However, when the data indicating that the accessoryis of the auto-aperture control type are fed thereto, the output fromthe decoder 44 is in a low level state. In addition, where no lensassembly is mounted on the camera body and, therefore, the data of"11100" for the check code are not fed to the register REG4, the ANDgate AN16 generates a low level output and the input to an OR gate 46 isbrought in a high level state. Accordingly, in the event that either thelens adaptor having no auto-aperture control linkage is used or theinterchangeable lens assembly is not coupled, the OR gate 46 generates ahigh level output. Since any aperture control need not be effected inthis case, this output is applied to the aperture control device 54 tobring the latter in an inoperative condition. In addition, since anydisplay need not be effected other than when the preset aperture valueis to be displayed, in the case of the T-priority mode and P-mode inwhich the aperture is automatically controlled, an AND gate 62 generatesa high level signal upon receipt of respective outputs from the OR gate46 and an OR gate 60, the output from the gate 62 being in turn fed tothe aperture display device 56 to bring the latter to an inoperativecondition.

With respect to the exposure time, where the lens adaptor is of a typehaving no auto-aperture control linkage, the output from the OR gate 46is in the high level state, and the mode selected is other than theM-mode (i.e., the output terminal M is in a low level state), an ANDgate 48 generates a high level signal. This high level signal is in turnapplied to a selection terminal SE of the multiplexer 42 and, in thiscase, the data of Ev-Avn fed from the adder 26 and based on the amountof light which has been reflected from the target object and measuredafter having passed through the aperture than manually preset, that is,the amount of light measured according to the stop-down measuringsystem, are outputed from the multiplexer 42 in the form as suppliedfrom the adder 26. Then, these data are displayed by the display device52 as a proper exposure time and, moreover, based on these data, theexposure time is controlled by the exposure time control device 50. Thatis to say, the aperture priority, automatic exposure time control modewith stop-down metering system is established. On the other hand, wherethe mode selected is the M-mode (that is, the output terminal M is in ahigh level state) while the output from the OR gate 46 is brought in ahigh level state, the AND gate 48 generates a low level signal. In thiscase, the multiplexer 42 outputs the data of the preset exposure timeTvs in the form as fed from the arithmetic circuit 40 and, accordingly,the display is controlled on the basis of these data Tvs. Where theoutput from the OR gate 46 is in a low level state, the display iscontrolled on the basis of the data fed from the arithmetic circuit 40.

FIG. 7 illustrate a circuit block diagram showing an exposure controlunit incorporated in the camera body and operable to effect an AE lockphotography based on the data corresponding to the amount of error inthe aperture read in a read-in unit in the camera body. Referencecharacter PD represents a photosensor positioned adjacent, for example,the plane at which a film is located and operable to effect a TTL lightmeasurement, that is, to measure the intensity of light reflected fromthe target object and then passed through the lens assembly. Referencenumeral 70 represents a light measuring circuit operable to output ananalog signal, the level of which corresponds to the intensity of lightdetected by the photosensor PD. Reference numeral 72 represents ananalog-to-digital converter for converting the analog signal, fed fromthe circuit 72, into a digital signal. The digital signal emerging fromthe converter 72 includes the amount of error ΔAv of the aperture of thezoom lens assembly as a phototaking lens assembly and, therefore,represents Bv-ΔAv-Avo. Reference numeral 74 represents a decoder forconverting the data of the minimum aperture value (the minimumF-number), which have been fed from the register REG5 shown in FIG. 5,into data Avo for arithmetic calculation. An adder 76 is operable to addthe data from the decoder 74 and those from the converter 72 together asshown by the following equation:

    (Bv-ΔAv-Avo)+Avo=Bv-ΔAv

Reference numeral 78 represents a decoder for converting the datacorresponding to the amount of error of the aperture, which have beenfed from the register REG12 (FIG. 1), into data ΔAv for the arithmeticcalculation, and an adder 80 performs a calculation of (Bv-ΔAv)+ΔAv=Bvon the basis of the data ΔAv and the data (Bv-ΔAv) fed respectively fromthe decoder 78 and the adder 76, thereby counterbalancing the datacorresponding to the amount of error of the aperture. Reference numeral24 represents a data output circuit for generating data Sv correspondingto the film speed set by a film speed setting member (not shown)incorporated in the camera body, and an adder 84 performs a calculationof Bv+Sv=Ev on the basis of the data Sv and the data Bv fed respectivelyfrom the data output circuit 24 and the adder 80. In this way, theproper exposure value Ev which is not affected by the amount of error ofthe aperture can be fed to an exposure arithmetic circuit 88. In thecase where the photo-taking lens assembly is not a zoom lens assembly,but a lens assembly of fixed focal length, since the amount of error ofthe aperture of such lens assembly, is zero, the output from theconverter 16 represents Bv-Avo, and since the register REG12 shown inFIG. 1 remains reset by the power-on reset signal POR, the decoder 78outputs the data indicating that the amount of error of the aperture iszero.

Reference numeral 86 represents a decoder for converting the data of thepreset aperture value, fed from the register REG10 shown in FIG. 1, intodata Avs for the arithmetic calculation, and reference numeral 36represents a data output circuit for outputing data Tvs corresponding tothe exposure time set by an exposure time setting member (not shown)incorporated in the camera body. The exposure arithmetic circuit 88 isoperable to perform an arithmetic calculation in accordance with theexposure value Ev from the adder 84, the minimum aperture value Avo fromthe decoder 74, the present aperture value Avs from the decoder 86, thepresent exposure time Tvs from the data output circuit 36, and the modedesignating signal from the exposure control mode setting device 38 aswill be described later. This mode setting device 38 has four outputterminals T, A, P and M corresponding to the four available exposurecontrol modes, which terminals are in turn connected to the arithmeticcircuit 88 and selectively feed the high level mode designating signalto the circuit 88 depending on which one of the control modes has beenselected. That is, when the T-priority mode in which the aperture isautomatically controlled according to the preset exposure time isselected, the output terminal T is brought in a high level state; whenthe A-priority mode in which the exposure time is automaticallycontrolled according to the present aperture is selected, the outputterminal A is brought in a high level state; when the P-mode in whichboth the exposure time and the aperture are automatically controlledaccording to a programed combination of these parameters, is selected,the output terminal P is brought in a high level state; and when theM-mode in which both the exposure time and the aperture are manuallycontrolled is selected, the output terminal M is brought in a high levelstate.

The arithmetic circuit 88 performs the following calculation when theoutput terminal T is in a high level state:

    Ev-Tvs=Av

    Av-Avo                                                     (7)

It performs the following calculation when the output terminal A is in ahigh level state:

    Ev-Avs=Tv

    Avs-Avo                                                    (8)

When the output terminal P is in the high level state, it performs thefollowing calculation:

    P·Ev=Av

    Av-Avo

    Ev-Av=Tv                                                   (9)

However, when the output terminal M is in a high level state, itperforms the following calculation.

    Avs-Avo                                                    (10)

From the arithmetic circuit 88, the data Tv of the preset or calculatedexposure time, the data Av-Avo of the calculated stop-down number, andthe data Av of the preset or calculated aperture value are fed to latchcircuits 90, 92 and 94, respectively.

A divider DI5 is adapted to be reset by the power-on reset signal PORgenerated in response to the closure of the light measuring switch S1and to receive the clock pulses CP from the oscillator PG shown inFIG. 1. This divider DI5 is operable to generate pulses at apredetermined cycle, for example, 16 Hz, upon receipt of the clockpulses from the oscillator PG, which are in turn fed to one-shot circuitOS11. The one-shot circuit OS11 generates a high level pulse in responseto the positive edge of the pulse of the predetermined cycle from thedivider DI5.

A D flip-flop DF15 is reset by the power-on reset signal POR and, whenand so long as the light measuring switch S1 remains closed, generates ahigh level signal from its Q output terminal in response to the positiveedge of the pulse from the one-shot circuit OS11 since the output fromthe inverter IN1 (FIG. 1) is in the high level state at this time. AnAND gate AN46 is enabled in response to this high level signal to allowthe pulses of the predetermined cycle from the one-shot circuit OS11 topass therethrough to the CL input terminal of a D flip-flop DF16 andalso to an AND gate AN47.

The D flip-flop DF16 is reset by the power-on reset signal POR andgenerates a high level output from the Q output terminal when a releaseswitch S3 adapted to be closed in response to the shutter releaseoperation and an AE lock switch S4 adapted to be closed in response tothe AE lock operation remain opened, that is, when none of the shutterrelease and AE lock operations is not effected. This is because theoutput from the AND gate AN46 is in the high level state. The AND gateAN47 is enabled in response to this high level output to allow thepassage of the pulses of the predetermined cycle therethrough to thelatch circuits 90, 92 and 94. These latch circuits 90, 92 and 94 thenoperate in response to these pulses to latch the respective data of theexposure time, the stop down number and the aperture value. Accordingly,when the light measuring switch S1 is closed, but the AE lock switch S4and the release switch S3 have not yet been closed, that is, only whenthe light measuring operation is carried out, the data from thearithmetic circuit 88 are successively latched in the latch circuits 90,92 and 94 according to the cycle (for example) 16 Hz) of the pulses fromthe one-shot circuit OS11. On the other hand, when the light measuringswitch S1 is subsequently opened, the output from the inverter IN1 isrendered in a low level state and the Q output from the D flip-flop DF15is consequently rendered in a low level state, thereby disabling the ANDgate AN16 to interrupt the passage of the latching signal from theone-shot circuit OS11 therethrough.

In the event that the AE lock switch S4 is closed during the closure ofthe light measuring switch S1, an OR gate OR15 is caused through aninverter IN11 to generate a high level signal and, when the read-inoperation of the data from the accessory has already been completed, anoutput from an AND gate AN48 is rendered in a high level state.Therefore, the Q output of the D flip-flop DF16 is rendered in a lowlevel state in response to the negative edge of the pulse, which is fedfrom the AND gate AN46 as the latching signal, and the AND gate AN47 isconsequently disabled to interrupt the passage of the latching signaltherethrough. Accordingly, the latch circuits 90, 92 and 94 latch theexposure information data in response to the last latching signalgenerated upon the closure of the AE lock switch S4 and the renewal ofthe data no longer take place.

When the release switch S3 is closed while the AE locked condition isestablished (with the Q output of the D flip-flop DF16 in the high levelstate), an inverter IN10 generates a high level signal and, where atthis time the read-in operation of the data from the accessory hascompleted with the "start" terminal being consequently in the high levelstate, an AND gate AN45 generates a high level output to cause aflip-flop FF45 to be set in response to the positive edge thereof,thereby rendering a terminal RL in a high level state. In response tothe positive edge of the terminal RL, a latch decoder 96 latches thedata of the amount of error of the aperture at the time of the closureof the release switch S3, which are fed from the register REG12 shown inFIG. 1, and then decode them into the data ΔAv2 for the arithmeticcalculation. At a subtractor 102, the following equation is calculated:

    Av-ΔAv2-Avo                                          (11)

In addition, in view of the terminal RL in the high level state, theflip-flop FF10 (FIG. 1) is set and the AND gate AN40 is consequentlydisabled with the result that the start signal no longer emerges fromthe AND gate AN40. After the lapse of a predetermined time determined bya delay circuit DL1 subsequent to the time when the terminal RL isbrought in a high level state, the delay circuit DL1 generates a highlevel output to trigger a release circuit 104 on, thereby initiating theexposure control operation. It is to be noted that during thepredetermined delay time, the availability of the electric power fromthe power source in the camera body and the presence or absence of acamera wobbling action are checked.

The aperture control device 54 is operable to stop down the aperturefrom the minimum aperture value by a value corresponding to the data fedfrom the subtractor 102, that is, by a value represented by Av-ΔAv2-Avo.Accordingly, the aperture when so stopped down is of a valuecorresponding to Av-ΔAv2, but since the amount of error at this time isΔAv2, the actual effective aperture is expressed by the followingequation:

    (Av-ΔAv2)+ΔAv2=Av                              (12)

and thus, it is controlled to the aperture value coinciding with aproper aperture value outputed from the arithmetic circuit 88 with anyinfluence from the amount of error Av1 at the time of the AE lockedcondition having been removed. On the other hand, a shutter controldevice 98 generates a low level output for a predetermined time based onthe data fed from the arithmetic circuit 88 and an electromagnet Mg isenergized in response to the low level output from the shutter controldevice 98 to interrupt a shutter closing operation thereby to controlthe exposure time. Thus, in the case where the exposure is controlled onthe basis of the AE lock, since the aperture control can be effectedafter the stop down number had been corrected to a value in which theamount of error of the aperture at the time of shutter release, theeffective aperture value can accurately be controlled to the calculatedor preset value. Accordingly, this invention is free from the problemheretofore encountered that the exposure error occurs when thephoto-taking is performed while the focal length of the zoom lensassembly is set to a different value at the time of the AE lock and theshutter release, respectively.

When the output from the shutter control device 98 is reversed to a highlevel state and the electromagnet Mg is consequently brought into anon-conductive state to initiate the shutter closing operation, anoutput CM of a delay circuit 100 is brought into a high level stateafter the lapse of a predetermined time determined by the delay circuit100. This signal is then fed through the OR gate OR10 (FIG. 1) to resetthe flip-flop FF10, thereby enabling the AND gate AN40 to initiate theread-in operation of the data from the accessory. The exposure timedisplay device 52 displays the exposure time on the basis of theexposure time data Tv fed from the latch circuit 90, whereas theaperture display device 56 displays the effective aperture valuecontrolled on the basis of the aperture data Av fed from the latchcircuit 94.

A normal photo-taking without any AE lock operation will now bedescribed. When the release switch S3 is closed subsequent to and duringthe closure of the light measuring switch S1, the output from theinverter IN10 is brought into a high level state and, where at this timethe "start" terminal is in a low level state as a result of completionof the read-in operation, the AND gate AN48 generates a high leveloutput. Therefore, the Q output from the D flip-flop DF16 is rendered ina low level state in response to the negative edge of the pulse from theAND gate AN46, thereby disabling the AND gate AN47 to interrupt thepassage of the latching signal therethrough. On the other hand, sincethe Q output from the D flip-flop DF16 is rendered in a high levelstate, the AND gate AN45 generates a high level signal with which theflip-flop FF45 is set and, consequently, the terminal RL is rendered ina high level state. Then, after the predetermined period of timedetermined by the delay circuit DL1, the release circuit 104 is operatedto initiate the exposure control operation. It is to be noted that, inthe event that the light measuring and release switches S1 and S3 aresubstantially simultaneously closed, the Q output from the D flip-flopDF16 is in a high level state and, therefore, one latching pulse canassuredly emerge from the AND gate AN47. This is also true even when theclosure of the release switch S3 is followed by the closure of the lightmeasuring switch S1, because the Q output of the D flip-flop DF16 is inthe high level state before the first latching pulse, which has beengenerated from the one-shot circuit OS11 subsequent to the resetting ofthe divider DI5 with the power-on reset signal POR resulting from theclosure of the light measuring switch S1, terminates. Accordingly, thereis no possibility that the exposure control operation will be initiatedbefore the exposure control information is latched in the latch circuits90, 92 and 94. This is also the case with the AE lock switch S4, andeven if the AE lock switch S4 is closed prior to the closure of thelight measuring switch S1, no latching takes place, but since the ANDgate AN47 is disabled after the first latching pulse has emerged fromthe AND gate AN47 as a result of the closure of the light measuringswitch S1 effected during the closure of the AE lock switch S4, theexposure control information data created at the time of the closure ofthe light measuring switch S1 are latched.

When the terminal RL is brought into a high level state, the latchdecoder 96 is latched with the data of the amount of error of theaperture fed from the register REG12, which are then converted into thedata ΔAv for the arithmetic calculation. At this time, the exposurecontrol information data based on the exposure value Ev free from theterm of the amount of error of the aperture included in the measuredlight output as hereinbefore described are latched in the latch circuit90, 92 and 94. In the subtractor 102, the following equation;

    Av-ΔAv-Avo                                           (11)

is calculated, and the aperture control device 54 stops down theaperture from the minimum aperture value in an amount corresponding tothese data. Accordingly, the aperture so stopped down corresponds toAv-Av, but since the amount of error of the aperture represents Av, theeffective aperture is expressed by the following equation and iscontrolled to a value coinciding with the aperture value outputed fromthe arithmetic circuit 88.

    (Av-ΔAv)+ΔAv=Av                                (12)

The display device 56 displays the effective aperture value socontrolled, and the exposure time is also displayed based on theexposure time calculated without being affected by the amount of errorΔAv of the aperture. Thus, any possible problem, heretofore encounteredthat, because the arithmetic calculation is performed with the measuredlight output including the amount of error ΔAv of the aperture, thecamera wobbing action tends to occur, can substantially be eliminated.

The method for correcting the amount of error of the aperture describedwith reference to FIG. 7 can be modified as follows. Namely, withoutcorrecting the amount of error of the aperture, the exposure valueEv-ΔAv is fed to the exposure arithmetic circuit 88, and the arithmeticcircuit 88 performs the following calculations:

In the case of the P-mode;

    p·(Ev-ΔAv)=Av-p·ΔAv

    Ev-ΔAv-(Av-p·ΔAv)=Tv-(1-p)·ΔAv

    Av-p·ΔAv-Avo                                (13)

In the case of the T-priority mode;

    Ev-ΔAv-Tvs=Av-ΔAv

    Av-ΔAv-Avo                                           (14)

In the case of the A-priority mode;

    Ev-ΔAv-Avs=Tv-ΔAv

    Avs-Avo                                                    (15)

Where the AE lock is effected, the exposure information data calculatedaccording to the equations (13), (14) and (15) are stored withoutupdating the latch circuits 90, 92 and 94, and the data ΔAv1 of theamount of error of the aperture is further stored. Then, the followingcalculations are performed:

In the case of the P-mode;

    (Av-p·ΔAv1)+p·ΔAv1=Av

    {Tv-(1-p)·ΔAv1}+(1-p)·ΔAv1=Tv

    Av-p·ΔA1-Avo+p·ΔAv1=Av-Avo   (16)

In the case of the T-priority mode;

    Av-ΔAv1+ΔAv1=Av

    Av-ΔAv1-Avo+ΔAv1=Av-Avo                        (17)

In the case of the A-priority mode;

    Tv-ΔAv1+ΔAv1=Tv                                (18)

After the shutter release, the data ΔAv2 of the amount of error of theaperture is stored, and the following equation is calculated so that theaperture can be controlled on the basis of the data so calculated whilethe exposure time is controlled on the basis of the calculated or presetexposure time data.

    Av-ΔAv2-Avo, Avs-ΔAv2-Avo                      (19)

The exposure control under the T-priority mode according to this methodwill now be described with reference to FIGS. 7 and 8.

FIG. 8 is a block circuit diagram showing only an essential portiondifferent from that shown in FIG. 7. The adder 84 calculates Ev-ΔAvbased on the data of Bv-ΔAv fed from the adder 76 and the film speeddata Sv fed from the data setting device 24 and supplies this data tothe exposure arithmetic circuit 88. At the time of the AE lock, the dataof Av-ΔAv1-Avo and Av-ΔAv1 are respectively stored in the latch circuits90 and 92, and the data ΔAv1 of the amount of error of the aperture fedfrom the register REG12 are latched in a latch decoder 106. These dataΔAv1 for the arithmetic calculation are fed to an adder 108 where theequation, (Av-ΔAv1)+ΔAv1, is calculated. The aperture display device 56displays the aperture value corresponding to the data Av. Subsequently,at the time of the shutter release, a subtractor 110 performs thecalculation of ΔAv1-ΔAv2 based on the data ΔAv2 of the amount of errorof the aperture then fed from the latch decoder 96 and the data ΔAv1 ofthe amount of error of the aperture at the time of the AE lock. The dataof the difference in amount of error of the aperture and the dataAv-Avo-ΔAv1 fed from the latch circuit 92 are fed to an adder 112. Then,the adder 112 performs the following calculation to give the dataAv-Avo-ΔAv2 with which the aperture is controlled.

    Av-Avo-ΔAv1+(ΔAv1-ΔAv2)=Av-Avo-ΔAv2 (20)

Although the data read-in circuit shown in FIGS. 1 and 3 is so designedthat the data of the amount of error of the aperture can be transmittedfrom the zoom lens assembly to the camera body it can be modified sothat the data of the amount of error of the aperture can beautomatically detected in the camera body based on other information ofthe zoom lens assembly. By way of example, the ROM in the circuitarrangement used in the camera body may be so constructed that, if theshortest and the longest focal lengths of the zoom lens assembly areknown, the camera body can understand what type of zoom lens assembly isbeing used. In such case, these data of the focal length can be utilizedto specify the highest significant bit of the address of the ROM in thecamera body while the preset focal length data may be used to specifythe least significant bit, thereby giving the amount of error of theaperture. If this construction is to be employed, it is enough for thelens assembly to transmit the data including the shortest focal length,the longest focal length and the preset focal length. Furthermore,instead of the shortest and the longest focal lengths, the dataindicative of the type of the lens assembly may be transmitted.

It is to be noted that, where the data from the subtractor 102 shown inFIG. 7 come to represent Av-ΔAv-Avo<0, the under exposure tends to occureven when the aperture of the lens assembly has been set to the minimumaperture value (the minimum F-number). In such case, it is recommendedto switch the mode over to the A-priority mode with Avo+ΔAv being usedas the preset aperture value to cause the arithmetic operation for theA-priority mode, thereby re-calculating the exposure time to becontrolled.

Even where the preset aperture value is Avo+ΔAv>Avs≧Avo, since it isimpossible to control the effective aperture value to Avs, thearithmetic and control operation has to be performed in a similar mannerwith Avo+ΔAv being used as the preset value while a warning ispreferably effected to inform the photographer that the control at Avsis impossible.

A zoom lens assembly of a type wherein the amount of error of theaperture varies, not with change in focal length such as hereinbeforedescribed, but with change in both of the focal length and the aperturevalue, for example, a zoom lens assembly wherein at the maximum aperturesetting the amount of error of the aperture varies with change in focallength, but at the minimum aperture setting the amount of error of theaperture is zero regardless of the focal length, is currentlycommercially available. With such a lens assembly, the address of theROM is preferably specified by the data corresponding to both of thefocal length and the aperture value so that the data of the amount oferror of the aperture can be outputted.

In addition, although in the foregoing description only the correctionof the amount of error of the aperture according to the adjustment ofthe focal length of the zoom lens assembly has been described, a lensassembly of a type wherein the effective aperture varies with rotationof a focusing ring which is a distance setting member of such lensassembly is also commercially available. Especially, in the case of alens assembly, for example, a macro lens assembly, wherein the shiftingamount is large, the effective aperture tends to vary considerably. Insuch case, the correction can be achieved if the amount of error of theaperture resulting from the focusing is made to be read from the lensassembly in the camera body as is the case with this invention.

In the foregoing description, the camera body has been described ashaving the lens assembly, for example, the zoom lens assembly or themacro lens assembly, coupled interchangeably thereto. However, it shouldbe noted that the concept of this invention can equally apply to thecamera body, having, for example, the zoom lens assembly, rigidly(non-interchangeably) coupled thereto. In addition, although the circuithas been described as constituted by a logic circuit for theillustration of this invention, the operation thereof may be programedso that a microprocessor (CPU) can sequentially control the operationaccording to the program stored therein.

Where flash photography is carried out by the use of an electronic flashunit in such a way that the flash control takes place by means of anelectronic flash unit so constructed as to interrupt the flashing whenthe integrated value of light measured by a light measuring circuitincorporated in the flash unit attains a predetermined valuecorresponding to a predetermined aperture value of the camera, or insuch a way as to utilize the fact that the product of thecamera-to-object distance times the aperture of the camera correspondsto the flash capacity (corresponding to a so-called "guide number") ofthe electronic flash unit, it is necessary for the aperture value of thephoto-taking lens assembly of the camera to be set at the predeterminedpreset value or the calculated value. Where the zoom lens assembly isused for the photo-taking lens assembly as is the case hereinbeforediscussed, may change in amount of error of the aperture resulting fromchange in focal length may result in deviation from the proper flashphotographing condition. The exposure control device according to thisinvention can be utilized even in such a case, and as an embodimentthereof, the photo-taking under the flash lighting wherein the aperturevalue is determined based on the amount of flash light Iv emitted fromthe electronic flash unit and the camera-to-object distance Dv will nowbe described with particular reference to FIG. 9.

FIG. 9 is a circuit block diagram showing a circuit construction suitedfor exposure control under flash lighting. Referring to FIG. 9, a dataoutput device 120 shown therein includes the register REG2 describedwith reference to and shown in FIG. 1 and is adapted to output distancedata Dv indicative of the distance between such device and the targetobject to be photographed, the minimum aperture value data Avo and thedata Av of the amount of error of the aperture. A calculator 124 for thecalculation of the aperture value for use in the photo-taking under theflash lighting condition performs the following calculation, using dataIv of the amount of flash light emitted from an electronic flash unit122, fed from the electronic flash unit 122, the distance data Dv fedfrom the data output device 120, and the film speed data Sv fed from thefilm speed data output device 24.

    Sv+Iv-Dv=Av

After this calculation, the calculator 124 generates data Av of theaperture value necessary to obtain a proper exposure. The aperture valuedata Av are displayed by an aperture display device 130 and are alsosupplied to a stop-down number calculator 126 for calculating thestop-down number. Since the stop-down number calculator 126 is suppliedwith the minimum aperture value data Avo, the stop-down number necessaryfor the control of the aperture to the proper aperture value Av can becalculated on the basis of the difference between the minimum aperturevalue data Avo and the aperture value data Av. It is to be noted thatthe minimum aperture value data Avo usually represent the minimumF-number at the shortest focal length. A correcting circuit 128 isoperable to calculate effective stop number data (Av-Avo-ΔAv) on thebasis of the stop-down number data (Av-Avo), obtained from the stop-downnumber calculator 126, and the data ΔAv fed from the data output device120. Based on the result of calculation performed by the correctingcircuit 128, an aperture control circuit 132 controls the aperture insuch a way as to counterbalance the data ΔAv of the amount of error ofthe aperture resulting from the stop-down of the aperture and to controlto an aperture size corresponding to the aperture value Av to becontrolled.

Although in the foregoing description the circuit shown and described isin the form of a logic circuit, the operation thereof may be soprogramed that a microprocessor (CPU) can sequentially control itaccording to such program stored therein.

For the purpose of reference, the problem which would arise when thisinvention is not adopted despite the fact that the zoom lens assemblyused is of a type wherein the amount of error of the aperture varieswith change in focal length will be discussed.

In the first place, in the case of the M-mode, the effective aperturevalue attributable to the controlled aperture size will be Avs+ΔAvwherein Avs represents the preset aperture value and ΔAv represents theamount of error of the aperture at a preset focal length of the zoomlens assembly. Accordingly, a problem arises in that the actual aperturevalue at the time of photo-taking will be the one smaller than thepreset aperture value by ΔAv, and the under exposure condition willoccur particularly where the preset aperture value and the presetexposure time are based on the reading of a separate exposure meterindependent from the camera. In the case of the A-priority mode, theeffective aperture value will be Bv-(Avo-ΔAv), wherein Avo representsthe minimum aperture value and Bv represents the brightness of thetarget object, because the data ΔAv of the amount of error of theaperture is included in the measured light output obtained through thethrough-the-lens metering system, and if the film speed is expressed bySv, the equation, Bv-(AVo+ΔAv)+Avo+Sv-Avs=Tv-ΔAv, is calculated based onthis measured light output. Therefore, at the time of the photo-taking,the aperture value is set to a value, AVs+ΔAv, smaller than the presetaperture value Avs by ΔAv while the exposure time remains at Tv-ΔAv. Insuch case, although the control is made to a proper exposure, theaperture is set at a value smaller than the preset value by ΔAv withcorresponding prolongation of the exposure time and there is a greatpossibility of the occurrence of the camera wobbling action. In the caseof the T-priority mode, the measured light output will be Bv-(Avo+ΔAv)as in the case under the A-priority mode and the equation,Bv-(Avo+ΔAv)+Avo+Sv+Tvs=Av-ΔAv, is calculated from this measured lightoutput. In such case, the term of ΔAv is counterbalanced at the time ofthe aperture control with the exposure time set to Tvs, resulting in thecontrol at the aperture value and the exposure time which are the sameas that when the amount of error of the aperture is zero. However, thereis a problem in that the aperture value displayed reads a value largerthan the controlled aperture value by ΔAv.

Moreover, in the case of the P-mode, the following equations:

    Bv-(Avo+ΔAv)+Avo+Sv=Ev-ΔAv

    p·(Ev-ΔAv)=Av-p·ΔAv

    (Ev-ΔAv)-(Av-p·ΔAv)=Tv-(1-p)·ΔAv

are calculated, and the aperture and the exposure time are controlled toAv+(1-p)·ΔAv (0<p<1) and Tv-(1-p)·ΔAv, respectively. Although thecontrol is made to a proper exposure even in this case, the aperturevalue displayed reads a value larger than the controlled aperture valueby p·ΔAv and the controlled exposure time is set to a value greater by(1-p)·ΔAv, resulting in the possible occurrence of the camera wobblingaction.

In addition thereto, the problem which would arise when, while the abovedescribed zoom lens is employed, the AE lock is performed without thisinvention being applied will now be described. Let it be assumed that,at the time the AE-lock is effected, the zoom lens assembly is set atthe shortest focal length and the amount of error of the aperture atthat time is zero. In this condition, assuming that the APEX value ofthe minimum aperture value is expressed by Avo and the APEX value of thebrightness of a particular portion of the target object at the time theAE lock has been effected is expressed by Bv, the measured light outputwill be Bv-Avo. Based on this value, one of the following equations (i),(ii) and (iii) is performed and the data of the exposure control value(the value of Av or Tv) so calculated is stored at the time of the AElock:

    (Bv-Avo)+Avo+Sv-Tvs=Av                                     (i)

    (Bv-Avo)+Avo+Sv-Avs=Tv                                     (ii)

    p[(Bv-Avo)+Avo+Sv]=Av

    Ev-Av=Tv                                                   (iii)

In these equations, Avs, Sv and Tvs represent the respective APEX valuesof the preset aperture value, the film speed, and the exposure time, Avand Tv represent the respective APEX values of the calculated aperturevalue and the calculated exposure time, and p represents a programconstant wherein 0<p<1. When the zoom lens assembly is, while the AElock is effected, manipulated to render the focal length to be adjustedtowards the longest focal length to frame the composition of the imageof the target object and the shutter is subsequently released bydepressing the shutter button, the aperture and the exposure time arecontrolled on the basis of the exposure control information set andstored at the time of the AE lock.

However, since the amount of error of the aperture varies from zero toΔAv (>0) as a result of change in focal length of the zoom lensassembly, the stop-down of the aperture based on the preset or storedaperture value will result in the actual aperture value reading Avs+ΔAvor Av+ΔAv. on the other hand, since the exposure time controlled remainsat a time corresponding to Tvs or Tv, there is a problem in that theexposure of that particular portion of the target object which has beenmeasured at the time of AE lock will be short of the required value byΔAv.

To generalize the above description concerning the problem which wouldarise without this invention applied, assuming that the amount of errorof the aperture at the focal length reading at the time of AE lock isΔAv1 and that reading at the time of the shutter release is ΔAv2, themeasured light output will be Bv-ΔAv1-Avo. Based on this value, one ofthe following equation (iv), (v) and (vi) is calculated and the exposurecontrol information so calculated is stored at the time of AE lock:

    (Bv-ΔAv1-Avo)+Avo+Sv+Tvs=Av-ΔAv1               (iv)

    (Bv-ΔAv1-Avo)+Avo+Sv-Avs=Tv-ΔAv1               (v)

    p·[(Bv-ΔAv1-Avo)+Avo+Sv]=Av-P·ΔAv1

    (Ev-ΔAv1)-(Av-P·ΔAv1)=Tv-(1-p)·ΔAv1 (vi)

When the zooming is effected to change the focal length while the AElock is effected and the shutter is subsequently released, the exposurecontrol will take place in the following manner. That is, where theequation (iv) is calculated, the aperture and the exposure time arecontrolled to ΔAv1+ΔAv2 and Tvs, respectively; where the equation (v) iscalculated, the aperture and the exposure time are controlled toAvs+ΔAv2 and Tv-ΔAv1, respectively; and where the equation (vi) iscalculated, the aperture and the exposure time are controlled toAv-p·ΔAv1+ΔAv2 and Tv-(1-p)·ΔAv1, respectively. Accordingly, in eithercase, the exposure results in error by an amount corresponding toΔAv2-ΔAv1.

However, according to this invention, it is clear that the foregoingproblems can be advantageously eliminated.

Another preferred embodiment of this invention will now be describedwith reference to FIGS. 10(a) and 10(b) which illustrate, in blockcircuit representation, a circuit incorporated in the camera body and acircuit incorporated in the lens assembly, respectively.

Referring first to FIG. 10(a), BA represents a battery power source, andMAS represents a manually operable power switch. When the switch MAS isclosed, an electrical power is supplied to both a microcomputer MCO andan oscillator OSC through a power line +E. In addition, the closure ofthe power switch MAS results in the operation of a power-on resetcircuit POR1 with a reset signal consequently fed from an outputterminal PO1 to a reset terminal RE of the microcomputer MCO to resetthe latter. The oscillator OSC, brought into operation upon closure ofthe power switch MAS generates, clock pulses which are in turn fed to aclock terminal CL of the microcomputer MCO. The clock pulses from theoscillator OSC are also fed to an exposure time control circuit TIC, anaperture control circuit APC, a release circuit RLC, and a mirrorrelease circuit MRC.

LMS represents a light measuring switch adapted to be closed upondepression of a shutter release button (not shown) through the firsthalf of the full stroke of movement of the shutter release button. Whenthis switch LMS is closed, an inverter IN50 generates a high levelsignal which is in turn fed to an input terminal i1 of the microcomputerMCO. Upon receipt of this high level signal applied to the inputterminal i1 the microcomputer MCO generates a high level signal from anoutput terminal O1 which is in turn fed to an inverter IN52 to cause thelatter to generate a low level signal. In response to this low levelsignal from the inverter IN52, a transistor BT50 is brought into aconducting state to effect the supply of the electric power to circuitcomponents other than the oscillator OSC and the microprocessor MCO andalso to the circuit in the lens assembly through a buffer BF, andcoupling terminals JB1 and JL1 by way of a power line +VF in the lensassembly.

When the supply of the electric power from the power line +V isinitiated upon conduction of the transistor BT50, a power-on resetcircuit POR2 is operated to generate a reset pulse from its outputterminal PO2, which is in turn fed to the exposure time control circuitTIC, the aperture control circuit APC, the release circuit RLC and themirror release circuit MRC to reset the latter.

LMC represents a light measuring circuit capable of generating ameasured light output which is an analog signal representing Bv-Avowherein Bv is the brightness of the target object and Avo is the minimumaperture value. This analog output is in turn fed to an analog inputterminal AN1 of the microcomputer MCO for the analog-to-digitalconversion. The microcomputer MCO has a reference potential inputterminal REV to which a reference potential for an analog-to-digitalconverter incorporated in the microcomputer MCO is applied from aconstant voltage source incorporated in the light measuring circuit LMC.

TIS represents a data output device for supplying data of the presetexposure time to an input port IP1 of the microcomputer MCO. APSrepresents a data output device for supplying data of the presetaperture value to an input port IP2 of the microcomputer MCO. FSSrepresents a data output device for supplying data of the preset filmspeed to an input port IP3 of the microcomputer MCO. MDS represents adata output device for supplying data of the present exposure arithmeticmode to an input port IP4 of the microcomputer MCO. DSP is a displayunit for displaying exposure control values, the contents to bedisplayed being controlled by a common terminal COM and a segmentterminal SEG both fed by the microcomputer MCO.

An output terminal O3 of the microcomputer MCO is connected to resetterminals RE of respective counters CO50 and CO52 (FIG. 10(b)) in thelens assembly through coupling terminals JB3 and JL3 (FIG. 10(b)). Thisoutput terminal O3 is in a high level state when the data are read outfrom the interchangeable lens assembly, thereby releasing the countersCO50 and CO52 from their reset states. A terminal SIC of themicrocomputer MCO is an output terminal through which, when couplingterminals JB2 and JL2 are connected together, the clock pulses are fedto the lens assembly for synchronizing at the time when the data areserially read in to a terminal SID of the microcomputer MCO. It is to benoted that the terminal JL2 is, as shown in FIG. 10(b), connected to aclock input terminal CL of the counter CO50 whereas the input terminalSID is connected with the output of an OR gate OR50 through couplingterminals JL5 and JB5.

FIG. 11 illustrate one example of a circuit of a serial data read-inunit associated with the terminals SIC and SID and incorporated in themicrocomputer MCO. FIG. 12 illustrate a chart showing the timing ofoperation of the circuit of FIG. 11. Referring now to FIG. 11, when aserial data read-in command SIIN is present, a flip-flop FF50 is set, asshown by a waveform FF50 Q in FIG. 12, and therefore, clock pulses DIC,which are the clock pulses fed from the oscillator OSC and subsequentlydivided in the microcomputer MCO, are allowed to pass through an ANDgate AN70 to the terminal SIC as shown by a waveform SIC in FIG. 12. Atthe same time, the clock pulses emerging from the AND gate AN70 are fedto respective clock terminals CL of a 3-bit binary counter CO60 and ashift register SR50. The shift register SR50 is operable to take in thedata from the terminal SID in response to the negative edge of each ofthe clock pulses fed to the clock terminal CL thereof.

In response to the positive edge of the eighth clock pulse, a carryterminal of the counter CO60 is rendered in a high level state as shownby a waveform CY in FIG. 12, and the output from an AND gate AN72 isrendered, as shown by a waveform AN72 in FIG. 12, in a high level statein response to the negative edge of the eighth clock pulse. Theflip-flop FF50 and the counter CO60 are in turn reset as shown by thewaveforms FF50 and CY in FIG. 12, and a serial data input flag SIFL isrendered in a high level state as shown by a waveform SIFL in FIG. 12,thereby completing the operation.

Referring back to FIG. 10(a), the switch RLS is a release switch adaptedto be closed during the depression of the release button through thelatter half of the full stroke of movement of the release button, and aswitch EXS is a switch adapted to be closed when the operation of anexposure control mechanism (not shown) completes, but opened when thecharging of the exposure control mechanism in readiness for the exposurecontrol operation completes. When the release switch RLS is closed whilethe output from an inverter IN56 is in a low level state as a result ofthe opening of the switch EXS subsequent to the completion of thecharging of the exposure control mechanism, a high level output emergesfrom an AND gate AN60. Since the output terminal of the AND gate AN60 isconnected to an interrupting terminal it of the microcomputer MCO, theexposure control operation is initiated when the interrupting terminalit of the microcomputer MCO is rendered in a high level state. Thistakes place no matter what operation the microcomputer MCO is thendoing. On the other hand, if the output from the inverter IN56 is in thehigh level state as a result of the closure of the switch EXS while thecharging of the exposure control operation has not yet been finished,the closure of the release switch RLS does not bring the output from theAND gate AN60 in a high level state and, therefore, the microcomputerMCO will not operate for the exposure control.

The microcomputer MCO has an output port OP1 from which exposure timedata Tv are outputed to the exposure time control circuit TIC; an outputport OP2 from which stop-down number data Av-Avo are outputed to theaperture control circuit APC; an output terminal O2 from which a pulseis outputed to the release circuit RLS for initiating the exposurecontrol operation; and an output terminal O4 from which a pulse isoutputed to the mirror release circuit MRC for initiating a mirror upmovement. It is to be noted that the input ports IP1 to IP4 and theoutput ports OP1 and OP2 of the microcomputer MCO may be replaced withcommon data buses so that the data transfer between the terminals TIS,APS, FSS, MDS, TIC and APC can take place on a time-sharing basis.

Referring now to FIG. 10(b), each of the counters CO50 and CO52 iscomprised of a 3-bit binary counter, the counter CO50 being operable tocount the number of positive edges of the clock pulses fed from theterminal SIC whereas the counter CO52 is operable to count the number ofnegative edges of pulses fed from a carry terminal CY of the counterCO50. Three-bit outputs h2, h1 and h0 of the counter CO50 are fed to adecoder DE50 which in turn generates the following signals, tabulated inTable 6, one at a time depending on the data fed from the counter CO50.

                  TABLE 6                                                         ______________________________________                                        CO50      Decoder DE50                                                        h2   h1    h0     e7   e6   e5   e4   e3   e2   e1  e0                        ______________________________________                                        0    0     0      H    L    L    L    L    L    L   L                         0    0     1      L    L    L    L    L    L    L   H                         0    1     0      L    L    L    L    L    L    H   L                         0    1     1      L    L    L    L    L    H    L   L                         1    0     0      L    L    L    L    H    L    L   L                         1    0     1      L    L    L    H    L    L    L   L                         1    1     0      L    L    H    L    L    L    L   L                         1    1     1      L    H    L    L    L    L    L   L                         ______________________________________                                    

Three-bit outputs g3, g2, g1 and g0 of the counter CO52 are fed to adecoder DE52 which in turn generates the following signals, tabulated inTable 7, one at a time depending on the data fed from the counter CO52.

                  TABLE 7                                                         ______________________________________                                        Counter CO52     Decoder DE52                                                 h5       h4    h3        g3  g2      g1  g0                                   ______________________________________                                        0        0     0         0   0       0   0                                    0        0     1         0   0       0   1                                    0        1     0         0   0       1   0                                    0        1     1         0   0       1   1                                    1        0     0         0   1       0   0                                    1        0     1         1   0       0   1                                    1        1     0         1   0       1   0                                    1        1     1         1   0       1   1                                    ______________________________________                                    

Of the output terminals of the decoder DE52, the terminal g3 isconnected to a select terminal SE of a data selector MP50, so that, whenthe terminal G3 is in a low level state, and in a high level state, thedata selector MP50 outputs input data fed to an input area d1 and inputdata fed to an input area d2, respectively, to a read-only memory RO50as address data. The input area d1 has its five most significant bitsgrounded and its three least significant bits connected with the outputterminals g2, g1 and g0 of the decoder DE52. Accordingly, when and solong as the output from the counter CO52 represents "000" to "100", theaddress of the ROM RO50 represented by "00000000" to "00000100" can besuccessively specified. The input area d2 has its three most significantbits connected with the output terminals g2, g1, and g0 of the decoderDE52 and its five least significant bits adapted to receive data fedfrom a code plate COD operatively associated with the focal lengthsetting member of the zoom lens assembly. The code plate COD referred toabove is of a construction substantially identical with that shown inFIG. 4. Accordingly, when and so long as the output from the counterCO52 represents "101" to "111", the address of the ROM RO50 representedby "001φφφφφ" to "011φφφφφ" can be specified successively. It is to benoted that the symbol "φ" represents a binary representation of either"1" or "0".

Hereinafter, data stored at each address of the ROM RO50 will bedescribed with reference to the following Table 8.

                  TABLE 8                                                         ______________________________________                                        Address     Significance                                                      ______________________________________                                        0 0 0 0 0 0 0 0                                                                           Zoom/Fixed Focal Length                                           0 0 0 0 0 0 0 1                                                                           Maximum Aperture Value Avo                                        0 0 0 0 0 0 1 0                                                                           Largest Aperture Value Av max                                     0 0 0 0 0 0 1 1                                                                           Shortest/Fixed Focal Length fw                                    0 0 0 0 0 1 0 0                                                                           Aperture Stabilized Time T1                                       0 0 1 0 0 0 0 0                                                                           Preset Focal Length fs                                            0 0 1 1 1 1 1 1                                                               0 1 0 0 0 0 0 0                                                                           Amount ΔAv of Change of the Effective                                   Aperture Value Resulting From Change                                          in Focal Length                                                   0 1 0 1 1 1 1 1                                                               0 1 1 0 0 0 0 0                                                                           Ratio Δf relative to Whole Capacity                                     of Preset Focal Length                                            0 1 1 1 1 1 1 1                                                               ______________________________________                                    

The ROM RO50 stores at the address of "00H" (H representing ahexadecimal digit) data of "F8H" in the case of the zoom lens assemblyand data of "F0H" in the case of the lens assembly of fixed focallength. Accordingly, if the camera body finds that none of these dataare read in the camera body, it determines that no interchangeable lensassembly is mounted and performs an exposure control under astopped-down metering mode. On the other hand, if it finds that one ofthese data has been read in, the exposure control takes place under afull open metering system.

At the address of "01H", the data of the minimum aperture value Avo arestored. In the case of the lens assembly of a type having its smallestF-number variable with change in focal length, the data of the smallestF-number are stored. At the address of "02H", the data of the largestaperture value Av max are stored. However, in the case of the lensassembly of a type wherein the largest F-number varies with change infocal length, the data of the smallest F-number are stored in a similarmanner. At the address of "03H", the data of the focal length in thecase of the lens assembly of fixed focal length, or the data of theshortest focal length in the case of the lens assembly of variable focallength, are stored. At the address of "04H", the data corresponding tothe time required for the aperture of the interchangeable lens assemblyto be stabilized at the smallest aperture subsequent to being stoppeddown (which time is hereinafter referred to as "release time lag") arestored. The data of the minimum aperture value Avo are used forcounterbalancing an element of the minimum aperture value included inthe measured light value, i.e., the calculation of (Bv-Avo)+Avo=Bv, forthe calculation of the stop-down number, i.e., Av-Avo, and also for thedetermination as to whether or not the aperture value Av iscontrollable. The largest aperture value Av max is used for thedetermination as to whether or not the aperture value Av iscontrollable. The data of the focal length are used for thedetermination as to whether or not the exposure time is a value likelyto result in the camera wobbling action, in the case of the lensassembly of fixed focal length. The data of the release time lag,although the details thereof will be described later, are used for thedetermination of the difference between the time of release of theexposure control mechanism and the time of release of a mirror-upmechanism so that, even when the aperture has been stopped down to themaximum aperture value, the exposure incident to the opening of theshutter can take place subsequent to the stabilization of the aperture.

In the case of the zoom lens assembly, at the addresses of "0010000" to"00111111", the data of the focal length corresponding to the data fromthe code plate COD are stored and can be used for the determination asto whether or not a warning of the possible occurrence of the camerawobbling action should be done. At the addresses of "01000000" to"01011111", the data ΔAv of the amount of change of the aperturecorresponding to the data from the code plate COD are stored. These dataare used for counterbalancing an element of the amount of change of theaperture included in the measured light value, i.e., the calculation of{Bv-(Avo+ΔAv)}+Avo+ΔAv=Bv, for the calculation, Av-(Avo+ΔAv),necessitated to control the effective aperture value of the lensassembly to an aperture value Av preset in the camera body, and for thedetermination as to whether or not the effective aperture value can becontrolled to the aperture value Av, i.e., Avo+ΔAv≦Av≦Av max+ΔAv. At theaddresses of "01100000" to "01111111", data of "01H" if the percentageof [(f-f min)/(f max-f min)]×100, wherein f, f min and f max representthe preset focal length, the shortest focal length and the longest focallength, respectively, is within the range of 0 to 15; data of "02H" ifit is within the range of 16 to 30; data of "04H" if it is within therange of 31 to 45; data of "08H" if it is within the range of 46 to 60;data of "10H" if it is within the range of 61 to 70; data of "20H" if itis within the range of 71 to 80; data of "40H" if it is within the rangeof 81 to 90; and data of "80H" if it is within the range of 91 to 100are stored in correspondence with the data from the code plate COD.These data are used to indicate the capacity of the zoom lens assemblyat which it is used. The foregoing are the data stored at the respectiveaddresses of the ROM RO50 and the purpose for which they are used.

FIG. 13 illustrates a timing chart showing the data read-in operationfrom the lens assembly to the camera body. The data read-in operationperformed from the lens assembly shown in FIG. 10(b) will now bedescribed with particular reference to FIG. 13. In the first place, whenthe output terminal O3 of the microcomputer MCO is set in a high levelstate, the counters CO50 and CO52 are released from the reset states.From the clock terminal SIC of the microcomputer MCO, 8 clock pulses areoutputed at each timing at which one byte data are read in in the mannerdescribed with reference to FIGS. 11 and 12. At the step So during whichthe initial data are read in, since the address of "00000000" of the ROMRO50 is specified, check data "F0H" or "F8H" are outputed, and theterminals e0 to e7 of the decoder DE50 are successively rendered in ahigh level state as the counter CO50 continues to count and AND gatesAN68 to AN61 are then successively enabled to permit the data fromoutput terminals f0 to f7 of the microcomputer MCO to pass therethroughsuccessively in the order from the least significant bit to the OR gateOR50 and then to the serial input terminal SID of the microcomputer MCOthrough the coupling terminals JL5 and JB5. The data so fed to the inputterminal SID are read into the shift register SR50 in the microcomputerMCO in response to the negative edge of the clock pulse identical withthe clock pulse fed from the terminal SIC, in the manner as hereinbeforedescribed with reference to FIGS. 11 and 12.

When the eighth clock pulse is fed to the counter CO50, the carryterminal CY thereof is rendered in a high level state in response to thepositive edge of such clock pulse, with the consequence that the step Sois shifted to the next succeeding step S1. When the clock pulse is againfed during the step S1, the carry terminal CY is rendered in a low levelstate in response to the positive edge of the clock pulse, and thecounter CO51 is, therefore, incremented by one in response to thenegative edge. Thus, the address of the ROM RO50 is specified by"00000001" fed from the input area d1 of the data selector MP50.

The foregoing operation is repeated until the step S4, and when thecarry terminal CY is rendered in a low level state at the end of thestep S4, the output of the counter CO52 becomes "101" and, therefore,the output from the decoder DE52 becomes "1001". Therefore, the dataselector MP50 specifies the address of "001φφφφφ" (It is to be notedthat "φφφφφ" constituting the five least significant bits representsdata from the code plate COD.) from the input area d2, and the data ofthe preset focal length stored at that address are read in themicrocomputer in a manner similar to that described hereinbefore. At thestep S6, the address of "010φφφφφ" is specified and the data of ΔAv areread in the microcomputer MCO. At the step S7, the address of "011φφφφφ"is specified and the data of Δf are read in the microcomputer MCO. Inthe manner as hereinbefore described, the data read-in operation in thecase of the zoom lens assembly completes and the output terminal O3 ofthe microcomputer MCO is rendered in a low level state with the countersCO50 and CO52 consequently reset. In the case with the lens assembly offixed focal length, the output terminal O3 of the microcomputer MCO isrendered in a low level state upon completion of the step S4, and thecounters CO50 and CO52 are reset, thus, completing the data read-inoperation from the lens assembly.

FIG. 14 illustrates a flow chart showing the sequence of operation ofthe microcomputer MCO. Hereinafter, the operation of the circuits shownin FIGS. 10(a) and 10(B) will be described with reference to the flowchart of FIG. 14. When the main switch MAS is closed, the supply of theelectric power from the battery power source BA to both themicrocomputer MCO and the oscillator OSC through the power line +E isinitiated and, at the same time, the microcomputer MCO, after havingbeen reset by the reset signal from the power-on reset circuit POR,waits for the time to come when the input terminal i, is brought in ahigh level state at the step #2 as a result of closure of the lightmeasuring switch LMS. When the input terminal i, is brought in the highlevel state, the output terminal O1 is brought in a high level state atthe step #3, thereby causing the transistor BT50 to conduct through theinverter IN52 with the result that the electric power supply through thepower line +V is initiated and, at the same time, the electric powersupply to the lens assembly through the buffer BF is initiated.Subsequently, the preset data from the input ports IP1, IP2, IP3 and IP4are successively taken in registers M0, M1, M2 and M3, respectively,thereby transferring to the step #8.

At the step #8, the output terminal O3 is rendered in a high levelstate, thereby releasing the counters CO50 and CO52 from the resetstates while a K register is set with 4H. At the step #10, aninstruction to read in the data serially is executed with the dataread-in operation from the lens assembly consequently initiated until acompletion flag SIFL becomes "1". When this flag SIFL subsequentlybecomes "1", the data taken in are set in a register Mk(M4 at first),and a register K determines as to whether or not they are "8H". If K isnot "8H", the register K is incremented by one and the process proceedsto the step #16 at which determination is made as to whether or not K is"CH". If K is not found "CH", the process returns to the step #10 toenable the next succeeding data read-in operation. After the abovedescribed operation has been repeated, and when K is determined "8H" atthe step #13, determination is made at the step #14 as to whether or notthe contents of the register M4 are "F8H". If they are not "F8H", itmeans that either the lens assembly of fixed focal length is mounted orany lens assembly is not mounted and, therefore, the process proceeddirect to the step #17 with no need for the microcomputer MCO to read inthe data. On the contrary thereto, if they are found to be "F8H", itmeans that the zoom lens assembly is mounted and, therefore, the processproceeds to the next step #15 to continue the data read-in operation.When K is found to become "CH" at the step #16, the process proceeds tothe step #17. Accordingly, the register M4 is set with a discriminationcode; the register M5 with Avo; the register M6 with Av max; theregister M7 with fw; the register M8 with the release time lag; theregister M9 with f; the register MA with ΔAv; and the register MB withΔf.

At the step #17, the terminal O3 is brought in a low level state and thecounters CO50 and CO52 are brought in reset state. At the step #18, theoutput from the light measuring circuit LMC is subjected to theanalog-to-digital conversion and the converted data are set in aregister Mc, and the exposure calculation is performed at the step #20.

Upon completion of the exposure calculation, the flag LMF is rendered 1and, at the step #22, determination is made as to whether or not a flagRLF is 1. If the flag RLF is found to be 1, the process proceeds to thestep #33, but if it is not found to be 1, the process proceeds to thestep #23 at which the exposure display is made. The function of the flagRLF will be described later.

At the step #24, discrimination is made as to whether or not the inputterminal i1 is in a high level state as a result of the closure of thelight measuring switch LMS. If the terminal i1 is in a high level state,the process returns to the step #2 to repeat the operation from the step#3. On the other hand, if the terminal i1 is found to be in a low levelstate at the step #24, the output terminal O1 is rendered in a low levelstate at the step #25 to interrupt the power supply through the powerline +V to the lens assembly. The display is a blank display with noinformation and, subsequently, after a light measurement flag LMF hasbeen set in 0 at the step #27, the process returns to the step #2 towait for the time to come when the light measuring switch LMS is againclosed.

When the release switch RLS is closed during the opening of the switchEXS subsequent to the completion of the charging of the exposure controlmechanism, the AND gate AN60 generates a high level signal with theinterrupting terminal it consequently rendered in a high level state. Asa result of this, the microcomputer MCO immediately starts the step #30irrespective of what step it has been occupied, thereby setting arelease flag RLF to 1 and, at the subsequent step #31, the outputterminal O3 is brought in a low level state as a countermeasure againstthe occurrence of the interrupting operation during the serial dataread-in operation. At the step #32, discrimination is made as to whetheror not the flag LMF is 1. If the flag LMF is not found to be 1, it meansthat the calculation to give the exposure control data has not yet beenfinished, and therefore, the process proceeds to the step #4 therebyinitiating the data read-in operation so that the exposure control datacan be calculated. In such case, since the release flag RLF is set to 1at the step #22, the step #22 shifts to the step #33.

If the flag LMF is found to be 1 at the step #32, the step #33 isinitiated to supply the data Tv for the control of the exposure timefrom the output port OP1 to the exposure time control circuit TIC, tosupply the data Av-Avo for the control of the stop-down number from theoutput port OP2 to the aperture control circuit APC, and to supply areleasing pulse from the terminal O2 to the release circuit RLC for theexposure control mechanism.

At the step #36, the microcomputer MCO waits for a time T1 correspondingto the data of the release time lag which have been taken in theregister M8. Thereafter, the releasing pulse is outputed from the outputterminal O4 to the mirror-up release circuit MRL, and then waits untilthe terminal i2 is brought in a high level state as a result of theclosure of the switch EXS subsequent to the completion of the exposurecontrol operation. When the input terminal i2 is brought in the highlevel state at the step #38, the flag RLF is set to 0 at the step #39and the process then proceeds to the step #24 so that, if the lightmeasuring switch LMS is not closed, the operation starting from the step#2 can be repeated, but if the switch LMS is closed, the power supply isinterrupted with the display erased, waiting, while the flag LMF is setto 0, for the time to come when the light measuring switch LMS iseventually closed.

FIG. 15 illustrates a time chart of the exposure control operation. Whenthe releasing pulse is outputed from the output terminal O2 of themicrocomputer MCO, the aperture is stopped down from the largestaperture and, after a time T1 subsequent to the generation of the pulsefrom the output terminal O2, a pulse emerges from the output terminal O4to initiate the mirror-up movement. Upon completion of the mirror-upmovement, an engagement of a leading curtain of the shutter is releasedby a mechanical structure to allow the leading curtain to travel and,after a time T4 subsequent to the start of travel of the leading shuttercurtain (It is to be noted that the time T4 corresponds to the time of2^(-Tv) counted by the exposure time control circuit TIC.), the trailingshutter curtain starts its travel.

If T1+T3≦T1+T2 wherein T2 is the time required to effect the mirror-upmovement, and T1+T3 is the time required for the aperture to bestabilized at the smallest aperture subsequent to the generation of thepulse from the terminal O2 and being stopped down to the smallestaperture, the aperture is assuredly stabilized at a time mt at which,subsequent to the start of travel of the leading shutter curtain, animage frame D is exposed to the incoming light through the lens assemblyand, therefore, there is no possibility of the occurrence of anyirregular exposure. Since the value of T1+T3 varies with the type of alens assembly, this variation can be compensated for if the time T1 isvaried according to the data of the release time lag, and in this case,the possible occurrence of any irregular exposure resulting from thedifference in speed at which the aperture is stopped can be eliminatedno matter what type of a lens assembly is mounted.

While the second preferred embodiment of this invention has fully beendescribed, it is to be noted that the above described ROM RO50 may storethe following data as fixed data. At the address of "00000101", the dataof the error in amount of light measured under the full open meteringsystem are stored, and the elimination of the error component includedin the measured light output is made on the basis of these data. At theaddress of "00000110", discriminating data necessary to discriminatewhether the lens assembly is of a type capable of being automaticallyfocused by means of a motor, built in the lens assembly, in response toan instruction fed from the camera, of a type capable of beingautomatically focused by means of a motor in the camera body, of a typecapable of being manually focused, or of a type unable to perform afocus detection based on the light reflected from the target object andpassing through the lens assembly, are stored. At the address of"00000111", a conversion coefficient K(N=K·ΔL) indicating the amount ofdrive N of the motor to be driven on the basis of a defocus amount ΔLfrom an automatic focus detecting device of the camera is stored. At theaddress of "00001000", data indicating the direction of rotation of themotor for shifting lens elements of the lens assembly are stored. At theaddress of "00001001", data of the amount of displacement Δ IR inposition of the focus relative to the visible rays of light when theautomatic focus detection performed by the camera is based on theinfrared rays.

On the other hand, in the case with the zoom lens assembly, since asfactors variable with change in focal length, there are K and ΔIR otherthan that described in connection with the foregoing embodiment, K andΔIR are to be stored at the address of "10000000" to "10011111" and atthe address of "10100000" to "10111111", respectively, so that K and ΔIRcorresponding to the preset focal length can be outputed depending onthe data from the code plate COD.

FIG. 16 illustrates the appearances of the camera body and the zoom lensassembly to which any one of the first and second embodiments of thepresent invention is practised. Reference numeral 150 represents afocusing ring, which, when rotated, causes a slide, similar to the slideVT shown in FIG. 4 and provided in the code plate 10 of FIG. 3 forproviding the distance data, to move in sliding engagement on thepatterned code. Reference numeral 152 represents a focal lengthadjusting ring which, when rotated, causes a slide, similar to the slideVT of FIG. 4 provided in the code plate COD of FIG. 10 or in the codeplate 12 of FIG. 3 for providing the focal length data, to move insliding engagement on the patterned code to provided from the code plate12 or COD the data corresponding to the preset focal length.

In the lens assembly, reference numeral 154 represents an annularabutment face provided with the coupling terminals JL1 to JL5 in anangular row. Reference numeral 156 represents a bayonet pawls andreference numeral 158 represents a stop-down pin. On the other hand, inthe camera body, reference numeral 160 represents a seat ring providedwith the coupling terminals JB1 to JB5 in an angular row so similar tothe angular row of the coupling terminals JL1 to JL5 that, when the lensassembly is mounted on or coupled to the camera body, the terminals JB1to JB5 can be electrically connected with the terminals JL1 to JL5.Reference numeral 162 represents bayonet flanges integral with the seatring 160, and reference numeral 164 represents an aperture stop-downcontrol member engageable with the stop-down pin 158.

When the lens assembly is to be mounted on the camera body, the lensassembly is inserted into the camera body until the abutment face 154contacts the seat ring 160. Subsequent rotation of the lens assemblyrelative to the camera body in a direction shown by the arrow Z resultsin clamping of the bayonet pawls 156 between the bayonet flanges 162 andassociated leaf springs (not shown) disposed rearwardly of the bayonetflanges 162, thereby to lock the lens assembly in position relative tothe camera body. At this time, the coupling terminals JB1 to JB5 areelectrically connected with the coupling terminals JL1 to JL5.

As hereinbefore described, the coupling terminals JB1 and JL1 are forsupplying the electric power from the camera body to the lens assemblytherethrough; the coupling terminals JB2 and JL2 are for supplying theclock pulses from the camera body to the lens assembly therethrough; thecouping terminals JB3 and JL3 are for supplying from the camera body tothe lens assembly therethrough the signal necessary to release thecircuit in the lens assembly from the reset state; the couplingterminals JB5 and JL5 are for transmitting the data from the lensassembly to the camera body therethrough; and the coupling terminals JB4and JL4 are common ground potential terminals.

We claim:
 1. In a camera system operable by means transmitting data froma camera accessory to a camera body, the camera accessorycomprising:means for storing various data at a plurality of addresses,respectively, the data each consisting of a plurality of bits; means forreceiving a train of clock pulses from a camera body; means forsequentially designating the addresses of said storing means one by oneto let said storing means output a data stored at the designatedaddress, including first means for originally forming at least a part ofan address signal within the camera accessory in response to the clockpulses received by said receiving means to designate an address; andmeans for transmitting the data derived from said storing means to thecamera body, whereby there is no necessity to receive a prepared addresssignal from the camera body.
 2. The camera accessory according to claim1, wherein the camera accessory consists of an interchangeable objectivelens.
 3. The camera accessory according to claim 1, wherein the cameraaccessory consists of a converter lens.
 4. The camera accessoryaccording to claim 1, wherein said first forming means includes acounter for counting the clock pulses received by said receiving meansto form the address signal in accordance with the count contents of saidcounter.
 5. The camera accessory according to claim 1 further comprisingmeans for manually setting photographic information at a value, whereinsaid designating means further includes second means for forming anaddress signal in response to said setting means.
 6. The cameraaccessory according to claim 5, wherein the camera accessory consists ofa zoom lens with a variable focal length, and the photographicinformation to be set by said setting means is the focal length.
 7. Thecamera accessory according to claim 6, wherein said storing means storesdata relating to the effective aperture value which varies in dependenceon the value of the focal length, the data being respectively stored indifferent addresses at every value of the focal length.
 8. The cameraaccessory according to claim 5, wherein said storing means stores aplurality of kinds of data each varying in dependence on the value ofthe photographic information to be set by said setting means, the databeing respectively stored in different addresses at every kind of dataand at every value of the photographic information, and wherein saidfirst and second forming means are cooperative to form one completeaddress signal to designate one address at which a data relating to adefinite kind and to a definite value of the photographic information isstored, the first forming means being definitive of the kind of data andthe second forming means being definitive of the value of thephotographic information.
 9. The camera accessory according to claim 1,wherein said transmitting means includes an initial part of a counterfor counting the train of clock pulses and said first forming meansincludes a succeeding part of the counter, said initial and succeedingparts serving as one serial counter with the initial part as its lowerbits and the succeeding part as its upper bits, in which the addresssignal formed by said first forming means is responsive to the countcontents of the succeeding part of said counter, and wherein saidtransmitting means further includes means for serially forwarding theplurality of bits of a data one by one in response to the count contentsof the initial part of said counter.
 10. The camera accessory accordingto claim 1, wherein the camera accessory consists of an interchangeableobjective lens having a variable diaphragm aperture, and wherein saidstoring means stores a data relating to a time taken for said variablediaphragm aperture to complete the variation of its aperture size. 11.In a camera system operable by means of carrying data, to a camera body,from a camera accessory consisting of an interchangeable objective lenswith a variable diaphragm aperture, the camera body comprising:means forreceiving from the camera accessory data relating to a time taken forthe variable diaphragm aperture to complete the variation of itsaperture size; means for transmitting driving power to the objectivelens to control the diaphragm aperture; means for controlling saiddriving power transmitting means to initiate the variation of theaperture size; a reflex mirror movable from a first position projectinginto a light path of the objective lens to a second position retractingtherefrom; and means for initiating the movement of said reflex mirrorfrom the first to the second position after the initiation of thevariation of the aperture size with a delay determined by the datareceived by said receiving means.
 12. In a camera system operable bymeans of transmitting data from a camera accessory to a camera body, thecamera accessory comprising:means for manually setting a photographicinformation at a desired value; means for storing various data at aplurality of addresses, respectively, said storing means storing aplurality of kinds of data each varying in dependence on the value ofthe photographic information to be set by said setting means, whereinthe data are respectively stored in different addresses for each kind ofdata and at every value of the photographic information; means forreceiving a digital signal from the camera body to determine the kind ofthe data; means for sequentially designating the addresses of saidstoring means one by one in response to the value set by said settingmeans and the digital signal received by said receiving means, to letsaid storing means output a data stored at the designated address; andmeans for transmitting the memory data derived from said storing meansto the camera body.
 13. The camera accessory according to claim 12,wherein said designating means includes means for forming a part of anaddress signal in response to the value set by said setting means and aremaining part of the address signal in response to the digital signalreceived by said receiving means, to complete one definite addresssignal.
 14. The camera accessory according to claim 13, wherein saiddigital signal received by said receiving means is a train of clockpulses transmitted from the camera, and wherein said forming meansincludes means for generating a digital code signal in response to saidsetting means to form the first mentioned part of an address signal andmeans for counting the clock pulses received by said receiving means toform the remaining part of the address signal in accordance with thecount contents of said counter, whereby one address signal is completedby means of a combination of the digital code signal and the countcontents of said counter.
 15. The camera accessory according to claim12, wherein the camera accessory consists of a zoom lens with a variablefocal length and the photographic information to be set by said settingmeans is the focal length.
 16. In a camera system operable by means ofcarrying data from a camera accessory consisting of an interchangeableobjective lens to a camera body combined with a lens converter, thecombination of the camera body and the lens converter comprising:meansfor receiving from the objective lens data representative of a fullyopen aperture value of the objective lens; means for measuring scenelight through the objective lens and the lens converter; first means forproviding an electric signal representative of a film speed of a film tobe used; second means for providing an electric signal relating to achange in an effective aperture value of the objective lens caused bythe combination of the lens converter with the camera body; and firstmeans for calculating a desired effective aperture value, which is freefrom the influence of the fully open aperture value and the change inthe effective aperture value caused by the combination of the lensconverter, in response to said receiving means, said measuring means andsaid first and second providing means.
 17. The combination of the camerabody and the lens converter according to claim 16 further comprisingsecond means for calculating information relating to steps ofstopping-down for realizing the desired aperture value in response tosaid receiving means, said second providing means and said firstcalculating means, and means for controlling an aperture size of theobjective lens in response to said second calculating means.
 18. In acamera system operable by means of carrying data from a camera accessoryto a camera body, the camera accessory consisting of a zoom lens with avariable focal length and a diaphragm aperture comprising:means formanually setting the focal length at a value; means for storing variousdata at a plurality of addresses, respectively, said storing meansstoring data relating to the effective aperture value which varies independence on the value of the focal length; means for receiving adigital signal from the camera body; means for receiving an electricpower from the camera body; means for designating an address of saidstoring means in response to said setting means to let said storingmeans output data stored at the designated address; means fortransmitting the data derived from said storing means to the camerabody; and means for receiving a driving power from the camera body tocontrol the diaphragm aperture.
 19. The camera accessory according toclaim 18, wherein the data stored in said storing means includeinformation respectively representative various deviations in theeffective aperture value at various focal lengths starting from aneffective aperture value at the shortest focal length.
 20. In a camerasystem operable by means of carrying data, to a camera body, from acamera accessory consisting of a zoom lens with a variable focal lengthand a diaphragm aperture, the camera body comprising:means fortransmitting a digital signal to the zoom lens; means for transmittingan electric power to the zoom lens; means for receiving data relating tothe effective aperture value, which varies in dependence on the value ofthe focal length, from the zoom lens; and means for transmitting drivingpower to the zoom lens to control the diaphragm aperture.
 21. The camerabody according to claim 20, further comprising means for generating asignal relating to a desired effective aperture value at which thediaphragm aperture is expected to be set, means for calculatinginformation relating to steps of stopping-down the diaphragm aperture,by which the desired effective aperture value is realized, in responseto said data received by said receiving means and said signal generatedby said generating means, and means for controlling said driving powertransmitting means in accordance with said information calculatingmeans.
 22. The camera body according to claim 21, wherein saidgenerating means includes means for manually setting the desiredeffective aperture value to generate said signal.
 23. The camera bodyaccording to claim 21, wherein said generating means includes means formeasuring scene light through the diaphragm aperture with its maximumsize, and means for calculating the desired effective aperture value togenerate said signal in response to said measuring means and said datareceiving means.
 24. The camera body according to claim 23, furthercomprising means for actuating the shutter release operation of thecamera, means for fixing the aperture value to be calculated by saideffective aperture value calculating means, and means for instructingsaid fixing means to function prior to the actuation of the shutterrelease operation, wherein said information calculating means isresponsive to said data received by said receiving means upon theactuation of the shutter release operation.
 25. The camera bodyaccording to claim 21, wherein said generating means includes firstmeans for providing data representative of a quantity of flash light tobe emitted upon flash photography, second means for providing datarepresentative of a photographic distance to an object to bephotographed, third means for providing a film speed of a film to beused, and means for calculating the desired effective aperture value togenerate said signal in response to said first to third providing means.26. The camera body according to claim 20 further comprising means formeasuring scene light through the diaphragm aperture with its maximumsize and means for generating a compensated exposure signal, which isfree from the change in the focal length, in response to said measuringmeans and said data receiving means.
 27. The camera body according toclaim 26 further comprising means for controlling the exposure time ofthe camera in response to said compensated exposure signal generatingmeans.
 28. The camera body according to claim 26 further comprisingmeans for actuating the shutter release operation of the camera, meansfor fixing the compensated exposure signal, means for instructing saidfixing means to function prior to the actuation of the shutter releaseoperation, and means for controlling the exposure in accordance withsaid compensated exposure signal fixed by said fixing means.
 29. In acamera system operable by means of carrying data from a camera accessoryto a camera body, the camera accessory consisting of an interchangeableobjective lens with a variable diaphragm aperture comprising:means forstoring electric data relating to a time taken for the variablediaphragm aperture to complete the variation of its aperture size; meansfor transmitting the electric data derived from said storing means tothe camera body; and means for receiving driving power from the camerabody to control the diaphragm aperture.
 30. The camera accessoryaccording to claim 29 further comprising means for receiving a digitalsignal from the camera body, and means for receiving electric power fromthe camera body to power said storing means, said transmitting means andsaid digital signal receiving means.
 31. In a camera system operable bymeans of carrying data, to a camera body, from a camera accessoryconsisting of an interchangeable objective lens, the camera bodycomprising:means for receiving the data from the objective lens; meansfor identifying a predetermined data to be received by said receivingmeans; an opening at which the objective lens is to be mounted; meansfor measuring light through said opening; means for providing a datarepresentative of a film speed of a film to be used; means for readingdata representative of a fully open aperture value of the objective lensto be received by said receiving means; and means for changing between afirst mode and a second mode of exposure operations in response to saididentifying means, wherein the exposure operation is responsive to saidmeasuring means, said providing means and said reading means in saidfirst mode when said identifying means succeeds in identifying saidpredetermined data, and to said measuring means and said providing meansin said second mode when said identifying means fails in identifyingsaid predetermined data.